Jamming satellitare: guerra aperta tra Iran e Europa, che spegne IRIB su Eutelsat

La guerra delle interferenze che aveva caratterizzato gli anni della Guerra fredda, epoca in cui tutte le nazioni dell'allora blocco sovietico disponevano di potenti impianti in grado di diffondere un rumore elettronico, il cosiddetto "jamming" sulle stesse frequenze a onde corte usate dalle emittenti occidentali, non ha mai visto un vero e proprio armistizio. Nazioni come Cina e Iran hanno sempre continuato a disturbare le emissioni "scomode", a carattere giornalistico, politico ma anche religioso. Oggi però che molte di quelle emittenti non trasmettono più sulle onde corte, preferendo Internet o il satellite, il conflitto ha fatto un salto di qualità. E anche le contromisure. 

Da mesi i maggiori broadcaster internazionali, con in testa la Voice of America, accusano nazioni come l'Iran di disturbare scientemente le emissioni radio satellitari agendo sulle frequenze (in GHz) degli "uplink", i collegamenti terra-satellite che vengono poi ridistribuiti dai "downlink" dei ripetitori orbitanti. All'inizio del 2012 era stata depositata una petizione in seno all'ITU, un appello firmato da British Broadcasting Corporation (BBC), Deutsche Welle (DW), Audiovisuel Extérieur de la France (AEF), Radio Netherlands Worldwide (RNW) and the U.S. Broadcasting Board of Governors (BBG). Quest'ultimo ha reiterato le sue richieste, precisando che ancora una volta gli iraniani erano intervenuti per bloccare alla fonte le trasmissioni satellitari di Radio Farda e Free Europe/Liberty. Già a febbraio l'ITU aveva reagito esortando i proprietari degli impianti di jamming al rispetto delle normative internazionali, che vietano espressamente i disturbi alle comunicazioni via satellite.

Oggi per la prima volta l'occidente reagisce. In seguito alle richieste dell'UE di inasprire le sanzioni contro il regime iraniano, Eutelsat, d'accordo con il regolatore francese, il CSA, ha deciso di spegnere il transponder di Hot Bird che ripeteva i programmi televisivi e radiofonici dell'IRIB (una emittente che diffonde anche programmi radiofonici in lingua italiana, utilizzando onde corte, il Web e il satellite). Gli iraniani non sono rimasti con le antenne in mano. Una petizione "per salvare la libertà di espressione in Europa" (non in Iran), è apparsa oltre che sul sito di Voce dell'Iran "Radio Italia" anche su Facebook. Andrea Borgnino annuncia che la questione verrà affrontata venerdì in diretta alle 11.30 da Radio 3, nel programma Radio3Mondo.

GLONASS, a lancio la navigazione sat made in Russia

Dopo lo sfortunato lancio del dicembre scorso, con il vettore inabissatosi nel Pacifico, il programma spaziale russo ha perfezionato il lancio di uno degli ultimi satelliti della costellazione GLONASS, il sistema di navigazione alternativo al GPS che opererà in analoghi segmenti della banda satellitare L. La costellazione è arrivata a 22 satelliti su 24 (più 2 o 3 di riserva). Contemporaneamente il mercato prepara il lancio dei dispositivi compatibili con il nuovo sistema di geoposizionamento. I cinesi delal ZTE forniranno infatti ad aprile un nuovo smartphone abilitato al GLONASS, che con il suo prezzo di circa 320 dollari, un terzo rispetto al prezzo dell'iPhone in Russia, punta a un grosso successo commerciale. La Russia vuole fare sempre più da sola nell'ambito dei servizi digitali, tanto è vero che in sede europea è stata anche fatta la proposta di un nuovo standard di radio digitale, il RAVIS, con cui i russi vogliono studiare la possibilità di digitalizzazione della banda FM.

Russia launches Glonass-K satellite

The Russian Space Forces have successfully launched a new Glonass-K navigation satellite from the Plesetsk space center, a Defense Ministry spokesman said Saturday.

The previous launch under the Glonass project in December 2010, supposed to conclude the forming of the satellite grouping, was unsuccessful as the rocket veered off course and sunk in the Pacific Ocean. The loss cost Russia 2.5 billion rubles ($86 million) in direct damages.

The Glonass satellite network is Russia's answer to the U.S. Global Positioning System, or GPS, and is designed for both military and civilian uses. Both systems allow users to determine their positions to within a few meters.

The Glonass-K, which has a service life of 10 years, will beam five navigation signals - four in the special L1 and L2 bands and one for civilian applications in the L3 band.

The complete grouping must have 24 operational and 2-3 reserve satellites for the Glonass network to operate with global coverage.

Russia currently has 22 Glonass satellites in orbit and will launch another three Glonass-M satellites on board a Proton heavy carrier rocket later this year to complete the Glonass grouping.

Glonass Smartphones Coming in April

21.02.2011

Mobile TeleSystems will begin selling its new Glonass-compatible smartphones in April, a month later than initially announced, and though it is technically less advanced than the iPhone, experts say, the new handset could easily outsell it in Russia.

The MTS Glonass 945, which AFK Sistema main owner Vladimir Yevtushenkov compared to the iPhone earlier this year, will sell for 11,000 rubles ($376) and will be the first smartphone to operate with the Russian navigation system, MTS spokeswoman Irina Osadchaya told The Moscow Times.

The new phone will be produced by ZTE, a major Chinese telecommunications equipment manufacturer, but the price for it may still be adjusted, the spokeswoman said.

When presented with the prototype of the phone late last year, Prime Minister Vladimir Putin joked that it would be good to have the phone ready by International Women's Day, so that Russian women, whom the holiday is supposed to celebrate, could find out where their husbands are.

"From the technical point of view, this smartphone is worse than the iPhone," said Vladimir Karpenko of J'Son & Partners. "The number of iPhones sold in Russia is quite small."

With the iPhone currently selling at 34,900 rubles, it constitute less than 1 percent of the market and will be easy to outsell, especially when the average cost of a cellular phone purchased by Russians is estimated at 4,100 rubles ($140) and smartphones at $320 to $330, Karpenko said.

Experts also point out that selling the new Glonass-compatible phone will require a substantial marketing effort, because the phone's main advantage is supposed to be its navigation system.

"People buy phones not for the sake of their navigation system," said Anna Lepetukhina, telecommunications analyst at Troika Dialog. "The phone is a bit too expensive if you just want to toy with the navigation system."

The Russian government has been cheerleading for Glonass and Yevtushenkov despite a carrier rocket with three Glonass-M satellites sinking in the Pacific Ocean on Dec. 5.

The government is now looking into introducing a 25 percent fee on GPS-only compatible equipment, and the Transportation Ministry has already drafted a bill to fine legal entities that own certain types of cars unequipped with Glonass up to 50,000 rubles.

Satellite Fermi: antimateria dai temporali

La missione orbitale Fermi, con a bordo un sistema di monitoraggio dei brillamenti gamma che arrivano dallo spazio, ha scoperto una inattesa sorgente gamma comunissima nella nostra atmosfera: i temporali. L'aspetto più incredibile è che le esplosioni di raggi gamma rilevate dalla sonda della NASA sono legate all'interazione tra materia e anti-materia. Nell'articolo che segue gli scienziati del Fermi spiegano che in caso di forti temporali le cariche determinano una improvvisa accelerazione degli elettroni che sovrastano le scariche atmosferiche. Una vera "valanga" di elettroni che sale verso lo spazio e interagendo con le molecole dell'atmosfera produce raggi gamma. A loro volta, i raggi investono nuovi elettroni, che accelerati generano altri raggi gamma in una esplosiva reazione a catena. Passando molto vicino ai nuclei degli atomi, i raggi gamma decadono in una coppia elettrone-positrone: l'elettrone e il suo equivalente in antimateria. Il laboratorio orbitale del Fermi ha potuto ricostruire il fenomeno perché il suo sistema di monitoraggio gamma ha rilevato raggi di una particolare intensità, circa mezzo milione di elettronVolt. La soglia rappresenta un preciso marker dell'interazione tra l'antimateria prodotta dai forti temporali (i positroni) e gli elettroni della sonda stessa. Ricombinandosi, positroni ed elettroni si annichiliscono a vicenda lasciandosi dietro una scia di altri raggi gamma a 511mila eV.

L'evento non è particolarmente raro, ma non si verifica con tutti i temporali. In circa tre anni Fermi ha misurato circa 130 brillamenti gamma di origine terrestre. Ora gli scienziati devono capire perché certe tempeste sono così speciali e determinare il ruolo dei fulmini come fattore scatenante della "valanga" che sfocia in produzione di antimateria. Mi chiedo se a loro volta i positroni e i raggi gamma prodotti dalla collisione tra materia e antimateria possono avere un effetto sulla ionosfera. Gli scienziati hanno per esempio descritto il fenomeno delle nubi noctilucenti, un effetto per certi versi simile alle aurore boreali e tra gli studiosi della ionosfera si ipotizza una possibile correlazione con fenomeni radiopropagativi speciali, come l'E sporadico. E se anche queste inattese centrali di produzione di antimateria fossero in qualche modo coinvolte?

Thunderstorms Make Antimatter

Jan. 11, 2011: Scientists using NASA's Fermi Gamma-ray Space Telescope have detected beams of antimatter produced above thunderstorms on Earth, a phenomenon never seen before.

Scientists think the antimatter particles were formed inside thunderstorms in a terrestrial gamma-ray flash (TGF) associated with lightning. It is estimated that about 500 TGFs occur daily worldwide, but most go undetected.

"These signals are the first direct evidence that thunderstorms make antimatter particle beams," said Michael Briggs, a member of Fermi's Gamma-ray Burst Monitor (GBM) team at the University of Alabama in Huntsville (UAH). He presented the findings Monday, during a news briefing at the American Astronomical Society meeting in Seattle.

Fermi is designed to monitor gamma rays, the highest energy form of light. When antimatter striking Fermi collides with a particle of normal matter, both particles immediately are annihilated and transformed into gamma rays. The GBM has detected gamma rays with energies of 511,000 electron volts, a signal indicating an electron has met its antimatter counterpart, a positron.

Although Fermi's GBM is designed to observe high-energy events in the universe, it's also providing valuable insights into this strange phenomenon. The GBM constantly monitors the entire celestial sky above and the Earth below. The GBM team has identified 130 TGFs since Fermi's launch in 2008.

"In orbit for less than three years, the Fermi mission has proven to be an amazing tool to probe the universe. Now we learn that it can discover mysteries much, much closer to home," said Ilana Harrus, Fermi program scientist at NASA Headquarters in Washington.

The spacecraft was located immediately above a thunderstorm for most of the observed TGFs, but in four cases, storms were far from Fermi. In addition, lightning-generated radio signals detected by a global monitoring network indicated the only lightning at the time was hundreds or more miles away. During one TGF, which occurred on Dec. 14, 2009, Fermi was located over Egypt. But the active storm was in Zambia, some 2,800 miles to the south. The distant storm was below Fermi's horizon, so any gamma rays it produced could not have been detected.

"Even though Fermi couldn't see the storm, the spacecraft nevertheless was magnetically connected to it," said Joseph Dwyer at the Florida Institute of Technology in Melbourne, Fla. "The TGF produced high-speed electrons and positrons, which then rode up Earth's magnetic field to strike the spacecraft."

The beam continued past Fermi, reached a location, known as a mirror point, where its motion was reversed, and then hit the spacecraft a second time just 23 milliseconds later. Each time, positrons in the beam collided with electrons in the spacecraft. The particles annihilated each other, emitting gamma rays detected by Fermi's GBM.

Scientists long have suspected TGFs arise from the strong electric fields near the tops of thunderstorms. Under the right conditions, they say, the field becomes strong enough that it drives an upward avalanche of electrons. Reaching speeds nearly as fast as light, the high-energy electrons give off gamma rays when they're deflected by air molecules. Normally, these gamma rays are detected as a TGF.

But the cascading electrons produce so many gamma rays that they blast electrons and positrons clear out of the atmosphere. This happens when the gamma-ray energy transforms into a pair of particles: an electron and a positron. It's these particles that reach Fermi's orbit.

The detection of positrons shows many high-energy particles are being ejected from the atmosphere. In fact, scientists now think that all TGFs emit electron/positron beams. A paper on the findings has been accepted for publication in Geophysical Research Letters.

"The Fermi results put us a step closer to understanding how TGFs work," said Steven Cummer at Duke University. "We still have to figure out what is special about these storms and the precise role lightning plays in the process."

ESA, le interferenze radio accecano i satelliti meteo

I dati climatici raccolti dai satelliti possono rivelarsi preziosi per il coordinamento delle misure contro l'inquinamento e il surriscaldamento del pianeta. Ma che succede se i sensori a bordo di queste sonde orbitanti non possono funzionare per colpa delle interferenze radio da terra? L'Agenzia spaziele europea ESA ha lanciato un vero e proprio allarme dopo essersi accorta dei problemi riscontrati con i sensori passivi a bordo del satellite SMOS, che misura l'umidità al suolo e la salinità degli oceani. Il sensore agisce in una porzione della banda L, tra 1400 e 1427 MHz, che in teoria dovrebbe essere protetta. E invece in molte zone il livello di interferenza RF da trasmissioni radar, televisive e radio è talmente elevato da accecare completamente lo strumento. La mappa pubblicata, in cui vengono evidenziate in rosso le aree più "calde" è abbastanza impressionante, il nostro meridione per esempio appare molto attivo.

L'ESA sta coordinando con le varie autorità locali una campagna di rilevamento al suolo con il preciso obiettivo di correggere questa situazione. Spesso, scrive il comunicato, si tratta semplicemente di risintonizzare gli apparati interferenti.

SMOS water mission winning battle with interference

6 October 2010

The results from ESA's SMOS satellite have been impressive, but the mission has been bugged by patches of interference from radar, TV and radio transmissions in what should be a protected band. Painstaking efforts to reduce these unwanted signals are now paying off.

Soon after the Soil Moisture and Ocean Salinity (SMOS) mission was launched, it was realised that, in some places, the data were being badly contaminated by radio-frequency interference – or RFI for short.

At times, this interference was effectively blinding the instrument, rendering the data over certain areas unusable. Nevertheless, SMOS was still clearly meeting its scientific requirements in areas free of RFI. However, to maximise the benefits of the mission the RFI issue needed to be addressed, which could only come about through international collaboration.

SMOS, also known as ESA's water mission, carries a passive radiometer that operates at 1400–1427 MHz in the L-band of the electromagnetic spectrum to capture snapshots of 'brightness temperature'. These snapshots correspond to microwave radiation being emitted from Earth's surface and relate to the amount of moisture in soil and salinity in the ocean. This information is needed to improve our understanding of Earth's water cycle.

According to radio regulations set by the International Telecommunications Union, this frequency band is reserved for the Earth Exploration Satellite Service, space research and radio astronomy. However, SMOS data revealed that there were many incidences of signals within this protected band, particularly in southern Europe, Asia, the Middle East and some coastal zones.

The transmissions contaminating the data were due to two main reasons: either emissions in adjacent bands that were leaking into the protected region owing to excessive power levels, or illegal transmissions within 1400–1427 MHz.

So far, the main culprits appear to be TV transmitters, radio links and networks such as security systems. Also terrestrial radars appear to cause interference.

To ensure that the excellence of the mission would not be compromised, ESA embarked upon the tricky and lengthy process of having the illegal transmissions shut down and the excessive out-of-band emissions reduced.

Tackling Europe first, this is being done case by case through cooperation with governments – and a significant number of sources of interference have already been eliminated.

The SMOS data are able to show, within a few kilometres, where the interference comes from. Knowing the rough locations, ESA has been contacting National Spectrum Management Authorities to request that they take steps to resolve the issue.

Mostly, the next stage involves the various authorities sending personnel into the field with sensors to identify the precise source of the signals.

In some cases, it's simply a matter of retuning the device to prevent the signal from leaking into the protected band or, more seriously, if the device is operating illegally the authorities have been shutting them down.

Over the last few months, ESA has been in touch with most European governments. Although it might seem a laborious process, cooperation between ESA and the National Spectrum Management Authorities has already led to a significant improvement so that RFI in the SMOS data is on the wane.

Spain is a particularly good example of this – the data are now much-improved with respect to RFI.

While the cooperation between ESA and governmental authorities continues to be fruitful, the hope is that these cases will lead to tighter regulation enforcement.

In pensione il primo "satellite dei satelliti" della NASA

Dopo più di un quarto di secolo di onorata carriera chiude la sua esistenza spaziale il satellite TDRS-1 o -A, un satellite molto speciale. Fin dalla sua iniziale messa in orbita dalla stiva dello Shuttle, nel 1983, il Tracking and Data Relay Satellite ha fatto da ponte tra la rete di rilevamento terrestre della NASA e una quantità infinita di altri satelliti e missioni spaziali, fornendo inoltre un prezioso supporto per il collegamento dei punti sulla terra che non possono stabilire connessioni dirette neppure attraverso i satelliti in orbita bassa, come i due poli geografici. Il geostazionario TDSR-1 è stato anche il primo satellite interconnesso a Internet.

A 27 anni di distanza non è più il solo. Il sistema TDRS consiste infatti in una decina di satelliti (per la verità il decimo è andato distrutto nel disastro del Challenger) e altri due se ne aggiungeranno entro il 2013. Considerata la messa in pensione del TDRS-1, in quell'anno si arriverà a una flotta di dieci.

Sulle comunicazioni in banda S, KA e KU rese possibili da questo network di ripetitori orbitali trovate una miriade di siti. E' opportuno partire da quello dedicato al 25esimo anniversario (2008) del TDRS-1 ma soprattutto dal bellissimo libro "Read you loud and clear" scritto per l'occasione da Sunny Tsiao. Una demo dell'interazione tra questi satelliti e la ground network della NASA si trova qui (richiesta l'applicazione di simulazione 3d Celestia). Altri siti offrono un quadro generale dei programmi di comunicazione spaziale e un dettaglio sul sistema geostazionario cui appartiene il TDRS-1, mentre questo è un sommario delle capacità di comunicazione:

S-Band Single Access - Full-time cover- age (except for a 10-minute gap per orbit over the Indian Ocean) provided by two 15- foot diameter steerable antennas used at the 2.0 to 2.3 GHz band supplies robust communications to user satellites with a smaller antenna, and receives telemetry data from expendable launch vehicles during launch.

Ku-Band Single Access - The same two large antennas, operating between 13.7 to 15.0 GHz, provide high data-rate support to the International Space Station with high- resolution digital television. The Ku-band also can dump huge volumes of data at rates up to 300 megabits per second (Mbps)

Ka-Band Single Access - This new higher-frequency (22.5 to 27.5 GHz) service increases data rate capabilities to 800 Mbps to provide communications with future missions requiring higher bandwidth communications such as multi-spectral instruments for Earth science applications.

Multiple Access - Using a phased array antenna and operating in the 2.0 to 2.3 GHz range, the system receives and relays data simultaneously from five lower datarate users and transmits commands to a single user.

Satellite Navigation - In addition to equipment located at the White Sands Complex in New Mexico, the system continues to provide user navigational data required to locate the orbit and position of NASA user satellites.

Ecco infine il comunicato sulla decommissionamento del Tracking and Data Relay Satellite numero 1, classe aprile 1983 e spento ufficialmente domenica 27 giugno 2010.

NASA RETIRES FIRST DATA RELAY SATELLITE AFTER STELLAR CAREER

WASHINGTON -- After a long and successful career providing communications support, NASA's groundbreaking Tracking and Data Relay Satellite (TDRS) 1 is retiring.

On Sunday, June 27, NASA will shut down the satellite that launched into orbit during space shuttle Challenger's maiden voyage (STS-6) in April 1983. From 1983 to 1998, TDRS-1 provided NASA with the ability to communicate with other satellites in orbit. NASA reassigned TDRS-1 in 1998 to support the National Science Foundation's (NSF) U.S. Antarctic Program and others on scientific, educational and operational endeavors.

TDRS-1 worked with eight additional satellites to relay data and communications from more than 15 customers, including the NSF, the Hubble Space Telescope, the shuttle and the International Space Station. The TDRS system provides the capability not only to send commands and receive data, but also to navigate and talk with crews in orbit.

"TDRS-1 paved the way for this incredible space communications system," said Bill Gerstenmaier, associate administrator for NASA's Space Operations Mission Directorate. "The remaining TDRS satellites, and the new satellites that will be online within three years, will carry on these critical capabilities for many NASA missions, including science and human spaceflight."

TDRS-1 was the first satellite used to support launches from NASA's Kennedy Space Center in Florida in the early 1990s, returning real-time telemetry. It eliminated a dead zone over the Indian Ocean where there previously was no communication, providing full coverage for the space shuttle and low-Earth orbiting satellites.

TDRS-1 proved helpful during a 1999 medical emergency at the NSF's Antarctic Amundsen-Scott South Pole Station. The satellite's high-speed Internet connectivity allowed personnel to conduct telemedicine conferences. Doctors in the United States aided Dr. Jerri Nelson, who had breast cancer, in performing a self-biopsy and administering chemotherapy. Later, in 2002, doctors used TDRS-1 to perform another telemedicine conference with the station to assist in knee surgery for a meteorologist.

Because of its orbit, the satellite was able to link the North and South Poles and relayed the first pole-to-pole phone call. TDRS-1 also transmitted the first internet connection and live webcast from the North Pole and supported the first global television event from the South Pole Station - a worldwide television broadcast to commemorate the beginning of the year 2000.

TDRS-1 was instrumental in supporting innovative astronomy and astrophysics research programs at the South Pole Station, including the one-of-a-kind IceCube Neutrino Observatory and the South Pole Radio Telescope. The satellite transmitted gigabytes of science research data to university researchers worldwide on a daily basis.

The first six TDRS satellites were built by TRW Inc. (now Northrop Grumman Corp.). Boeing Space and Intelligence Systems also built three TDRS satellites. NASA plans to launch two additional satellites into the Tracking and Data Relay Satellite System by 2013. On June 13, 2010, the satellite arrived at its final destination, approximately 22,500 miles above the Earth. After the orbit is stabilized and the remaining fuel removed, NASA will shut down the satellite on Sunday, June 27.

http://nssdc.gsfc.nasa.gov/multi/tdrs.html

Svelata l'orbita segreta dello shuttle-spia

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Un velivolo orbitale senza pilota a bordo che parte da Cape Canaveral ma nessuno sa dove sta andando, o a fare che cosa. Ed ecco arrivare, come racconta il New York Times, l'intrepida combriccola di cacciatori di satelliti di SatObs.org e il velivolo pensato come sostituto dello Shuttle ma gestito oggi come un esperimento militare, viene individuato e la sua orbita segreta calcolata.

Il Boeing X-37B, lanciato il 22 aprile con un missile Atlas V per la missione siglata USA-212, è incluso nella lista di satelliti artificiali, alcuni dei quali spionistici, della nuova applicazione iPhone Satellite Flybys, sviluppata per il sito Spaceweather.com. Il costo è di 2 dollari e 39 e il programma molto semplice individua la posizione dell'osservatore e fornisce tutte le indicazioni per l'osservazione visuale, aggiungendo schede e notizie sui vari satelliti selezionati al momento. Anche il sito Heavens-Above propone lo stesso tipo di informazioni, gratuitamente. Inizialmente il capofila del progetto X-37 era la NASA, ma qualche anno fa l'incartamento è stato trasferito al DARPA.

Doveva essere uno Shuttle molto più piccolo e leggero, tanto che nei primi tempi si pensava di trasportarlo in orbita proprio con la navetta. Poi è stato ritenuto più opportuno, malgrado le ridotte dimensioni, agganciarlo a un razzo vettore. Che cosa sta facendo l'X-37B da un mese a questa parte nella sua orbita bassa? L'Aviazione USA ha parlato molto genericamente di verifiche sperimentali per il suo Orbital Test Vehicle-1, ma l'inclinazione orbitale dello shuttle militare lo porta del tutto casualmente alle latitudini dell'Iran, dell'Afghanistan e della Corea. E' possibile ricavare dati utili da un aereo che viaggia a quote tanto elevate? Ci vorrebbero i militari per dirlo.

Intanto l'attivismo degli astronomi dilettanti conferma ancora una volta che i segreti non reggono a lungo di questi tempi. Senza nessuno a bordo le comunicazioni con l'X-37B possono evidentemente fare a meno della voce, ma immagino che ci sia parecchia comunicazione strumentale e telemetria, oltre naturalmente all'imaging. Spero che almeno questo segreto riescano a custodirlo. Sul lato trasmissivo si sa solo della commessa vinta da Quintron per la fornitura dei sistemi di comunicazione a terra per la missione USA-212.

Surveillance Suspected as Spacecraft’s Main Role

A team of amateur sky watchers has pierced the veil of secrecy surrounding the debut flight of the nation’s first robotic spaceplane, finding clues that suggest the military craft is engaged in the development of spy satellites rather than space weapons, which some experts have suspected but the Pentagon strongly denies.

Last month, the unmanned successor to the space shuttle blasted off from Florida on its debut mission but attracted little public notice because no one knew where it was going or what it was doing. The spaceship, known as the X-37B, was shrouded in operational secrecy, even as civilian specialists reported that it might go on mysterious errands for as long as nine months before zooming back to earth and touching down on a California runway.

In interviews and statements, Pentagon leaders strongly denied that the winged plane had anything to do with space weapons, even while conceding that its ultimate goal was to aid terrestrial war fighters with a variety of ancillary missions. The secretive effort seeks “no offensive capabilities,” Gary E. Payton, under secretary of the Air Force for space programs, emphasized on Friday. “The program supports technology risk reduction, experimentation and operational concept development.” The secretive flight, civilian specialists said in recent weeks, probably centers at least partly on testing powerful sensors for a new generation of spy satellites.

Now, the amateur sky watchers have succeeded in tracking the stealthy object for the first time and uncovering clues that could back up the surveillance theory. Ted Molczan, a team member in Toronto, said the military spacecraft was passing over the same region on the ground once every four days, a pattern he called “a common feature of U.S. imaging reconnaissance satellites.” In six sightings, the team has found that the craft orbits as far north as 40 degrees latitude, just below New York City. In theory, on a clear night, an observer in the suburbs might see the X-37B as a bright star moving across the southern sky. “This looks very, very good,” Mr. Molczan said of the identification. “We got it.”

In moving from as far as 40 degrees north latitude to 40 degrees south latitude, the military spacecraft passes over many global trouble spots, including Iraq, Iran, Afghanistan, Pakistan and North Korea. Mr. Molczan said team members in Canada and South Africa made independent observations of the X-37B on Thursday and, as it turned out, caught an earlier glimpse of the orbiting spaceship late last month from the United States. Weeks of sky surveys paid off when the team members Kevin Fetter and Greg Roberts managed to observe the craft from Brockville, Ontario, and Cape Town. Mr. Molczan said the X-37B was orbiting about 255 miles up — standard for a space shuttle — and circling the planet once every 90 minutes or so.

A fair amount is known publicly about the features of the X-37B because it began life 11 years ago as a project of the National Aeronautics and Space Administration, which operates the nation’s space shuttles. The Air Force took over the program in 2006, during the Bush administration, and hung a cloak of secrecy over its budget and missions.

The X-37B has a wingspan of just over 14 feet and is 29 feet long. It looks something like a space shuttle, although about a quarter of the length. The craft’s payload bay is the size of a pickup truck bed, suggesting that it can not only expose experiments to the void of outer space but also deploy and retrieve small satellites. The X-37B can stay aloft for as long as nine months because it deploys solar panels for power, unlike the space shuttle.

Brian Weedon, a former Air Force officer now with the Secure World Foundation, a private group based in Superior, Colo., said the duration of the X-37B’s initial flight would probably depend on “how well it performs in orbit.” The Air Force Rapid Capabilities Office leads the X-37B program for what it calls the “development and fielding of select Defense Department combat support and weapons systems.” Mr. Payton, a former astronaut and senior NASA official, has acknowledged that the spacecraft is ultimately meant to give the United States new advantages on terrestrial battlefields, but denies that it represents any kind of space weaponization.

On April 20, two days before the mission’s start, he told reporters that the spacecraft, if successful, would “push us in the vector of being able to react to war-fighter needs more quickly.” And, while offering no specifics, he added that its response to an “urgent war-fighter need” might even pre-empt the launching of other missions on expendable rockets. But he emphasized the spacecraft’s advantages as an orbiting laboratory, saying it could expose new technology to space for a long time and then “bring it back” for inspection.

Mission control for the X-37B, Mr. Payton said, is located at the Air Force Space Command’s Third Space Experimentation Squadron, based at Schriever Air Force Base in Colorado Springs. He added that the Air Force was building another of the winged spaceships and hopes to launch it next year. The current mission began on April 22, when an Atlas 5 rocket at the Cape Canaveral Air Force Station in Florida fired the 5.5-ton spacecraft into orbit.

Jonathan McDowell, a Harvard astronomer who tracks rocket launchings and space activity, said the secrecy surrounding the X-37B even extended to the whereabouts of the rocket’s upper stage, which was sent into an unknown orbit around the sun. In one of his regular Internet postings, he said that appeared to be the first time the United States had put a space vehicle into a solar orbit that is “officially secret.”

David C. Wright, a senior scientist at the Union of Concerned Scientists, a private group in Cambridge, Mass., said many aerospace experts questioned whether the mission benefits of the X-37B outweighed its costs and argued that expendable rockets could achieve similar results. “Sure it’s nice to have,” he said. “But is it really worth the expense?” Mr. Weedon of the Secure World Foundation argued that the X-37B could prove valuable for quick reconnaissance missions. He said ground crews might rapidly reconfigure its payload — either optical or radar — and have it shot into space on short notice for battlefield surveillance, letting the sensors zoom in on specific conflicts beyond the reach of the nation’s fleet of regular spy satellites.

But he questioned the current mission’s secrecy. “I don’t think this has anything to do with weapons,” Mr. Weedon said. “But because of the classification, and the refusal to talk, the door opens to all that. So, from a U.S. perspective, that’s counterproductive.” He also questioned whether the Pentagon’s secrecy about the spacecraft’s orbit had any practical consequences other than keeping the public in the dark. “If a bunch of amateurs can find it,” Mr. Weedon said, “so can our adversaries.”

Radio girrrls

Una bella scoperta grazie a Benn Kobb, da Washington DC. Questa è Diana Eng, radioamatrice di Brooklyn, NY, autrice del blog Fashion Nerd (e di un recente libro sulla moda high-tech). Nella foto Diana mostra la sua antenna Yagi "pieghevole" per comunicazioni VHF/UHF satellitari. Le istruzioni per la realizzazione (servono il saldatore e la macchina per cucire) si trovano sul sito della rivista Makezine. Diana mi ha fatto scoprire una azienda di kit per autocostruzioni elettroniche, Adafruit, fondato da un'altra giovane ragazza, l'ingegner Limor Fried.

Un telescopio spaziale per il nostro sole mutevole

Non ce ne accorgiamo, dicono gli scienziati della NASA, ma il nostro sole è una stella variabile, una continua fabbrica di fenomeni misteriosi, un vero e proprio laboratorio di astrofisica. Per studiarla, per cercare di capire tutte le conseguenze della sua dinamicità sulla nostra atmosfera e probabilmente il nostro clima, sta per essere lanciata, il 9 febbraio l'ambiziosa missione del Solar Dynamics Observatory. Che ha anche aperto un fantastico canale su You Tube.

Solar Dynamics Observatory: The 'Variable Sun' Mission
02.05.2010

February 5, 2010: For some years now, an unorthodox idea has been gaining favor among astronomers. It contradicts old teachings and unsettles thoughtful observers, especially climatologists. "The sun," explains Lika Guhathakurta of NASA headquarters in Washington DC, "is a variable star." But it looks so constant... That's only a limitation of the human eye. Modern telescopes and spacecraft have penetrated the sun's blinding glare and found a maelstrom of unpredictable turmoil. Solar flares explode with the power of a billion atomic bombs. Clouds of magnetized gas (CMEs) big enough to swallow planets break away from the stellar surface. Holes in the sun's atmosphere spew million mile-per-hour gusts of solar wind. And those are the things that can happen in just one day.
Over longer periods of decades to centuries, solar activity waxes and wanes with a complex rhythm that researchers are still sorting out. The most famous "beat" is the 11-year sunspot cycle, described in many texts as a regular, clockwork process. In fact, it seems to have a mind of its own.
"It's not even 11 years," says Guhathakurtha. "The cycle ranges in length from 9 to 12 years. Some cycles are intense, with many sunspots and solar flares; others are mild, with relatively little solar activity. In the 17th century, during a period called the 'Maunder Minimum,' the cycle appeared to stop altogether for about 70 years and no one knows why."
There is no need to go so far back in time, however, to find an example of the cycle's unpredictability. Right now the sun is climbing out of a century-class solar minimum that almost no one anticipated.
"The depth of the solar minimum in 2008-2009 really took us by surprise," says sunspot expert David Hathaway of the Marshall Space Flight Center in Huntsville, Alabama. "It highlights how far we still have to go to successfully forecast solar activity."
That's a problem, because human society is increasingly vulnerable to solar flare ups. Modern people depend on a network of interconnected high-tech systems for the basics of daily life. Smart power grids, GPS navigation, air travel, financial services, emergency radio communications—they can all be knocked out by intense solar activity. According to a 2008 study by the National Academy of Sciences, a century-class solar storm could cause twenty times more economic damage than Hurricane Katrina.
(continua)

Un sole a bassa energia potrebbe essere normale

Ho scoperto grazie a una delle tante mailing list che frequento un'altra interessante fonte di informazione sull'attività solare e sulle teorie legate ai suoi meccanismi più attivi, dai brillamenti (flares) alle eiezioni di massa coronale. Si tratta del wiki curato dal team di ricercatori di RHESSI la missione satellitare lanciata nel 2002 per studiare spettroscopicamente i fenomeni solari ad alta energia.
Leif Svalgaard e Hugh Hudson si chiedono se non sia il caso, per chi studia questi fenomeni, di cominciare a preoccuparsi visto che il prolungato minimo solare ha drasticamente ridotto il numero di brillamenti da un sole caratterizzato da lunghi periodi senza macchie. Non solo, anche il flusso alla lunghezza d'onda di 10,7 centimetri appare in costante calo, segno di un abbassamento di quella che potremmo definire attività corrente del sole. La conclusione, dicono i ricercatori, è che no, non è ancora il caso di spaventarsi, perché abbiamo ampia evidenza storica di un sole ancora meno attivo di così. Semmai sono stati gli ultimi cicli, quelli immediatamente precedenti il numero 24 a essere stati particolarmente agitati. La transizione tra l'ultimi ciclo e l'attuale appena iniziato ricorderebbe condizioni riscontrate poco più di un secolo fa, nel passaggio dal ciclo 13 al 14. Naturalmente i dati raccolti allora erano diversi e non prevedevano misurazioni del flusso a 10,7 centimetri.
L'indirizzo del wiki è questo (per leggere gli articoli cliccare su "nuggets"). La pagina del RHESSI dell'Università di California a Berkeley si aggiunge a quella del Goddard Space Center della NASA dove si trovano molti dati raccolti dalla sonda.

Cycle 24 - don't panic yet!
From RHESSI Wiki

Published: 13 April 2009
Leif Svalgaard and Hugh Hudson

We're in an extended period of minimal solar activity (see Nugget 91 for a previous look at this issue). Without flares, RHESSI is missing its most important observational work, and there has not been even a C-class flare yet this year. Will sunspots and flares ever return? How unusual is this behavior? In this Nugget we conclude that it is too soon to panic, but that certainly we're seeing an interesting diminished level of activity -a level most of us have not seen before.
The 10-cm radio flux from the Sun, with its daily index F10.7, is one of the basic standard tools for gauging the level of solar activity. This index has been generated in an unbroken string since 1947. It is derived from careful radio flux measurements made in Canada and pioneered by the early radio astronomer A.E. Covington.
The figure on the left might give cause for alarm if one is interested in observations of solar flares. It shows (red line) the variation of F10.7 monthly means for the two years prior to the present time. The black line shows the mean of the four previous cycles, registered by summed epoch analysis on simple Gaussian fits to their preceding maxima as references. The four time series from prior maxima from are averaged, using the Gaussian peak time as a reference, month by month; the range bars show the standard deviations of these means for each month. This procedure does not allow for the possibility of different cycle durations, something that seems fairly obvious from the sunspot record, but it is hard to be quantitative about this. Our approach here is to use the most direct approach to analysis of the most objective of the indices, and Figure 1 is the result. If one interprets the range bars as true error bars, and did not know (or believe) that cycles could have different lengths, this figure would provide compelling evidence that Cycle 24 is special, and that it might be time for fans of solar flares to "panic." Our discussion below, however, shows that this would be premature.
A closer look (Figure 2 below) shows the daily values of three indices: F10.7, the total solar irradiance TSI, and the classical sunspot number. There is a clear apperance of an up-turn in the least "noisy" of these indices, F10.7, although there are other small variations that we do not understand well. But probably F10.7 is giving us an early warning about the sudden increase of Cycle 24 spots. These should appear within the next few weeks or months, though, so please check the daily updates of the indices on our Web page.
In Figure 3 we do a comparison of the contributions of old- and new-cycle activity to the minimum periods between Cycles 21/22, 22/23, and 23/24 (the present one). These are counts of 'region days' per month (normalized to 30 days), defined as the number of days when an active region (one with a NOAA number) was visible within 70 degrees of central meridian, and then summed for every region. Different cycles (as determined from the magnetic polarity of the spots) are coded with a different color. Yearly smoothed counts are shown as the 'smoother' curves. The detailed bottom three panels show blown-up views of the transitions between cycles. Note that the 23/24 transition is indeed diffferent, and that Cycle 24 has just barely begun (see also the weak increase in F10.7 visible in Figure 2).
Although this transition may look unusual to us, for the Sun it may just be business as usual. The current transition looks very much like the one between cycles 13 and 14, 107 years ago. Not only were the sunspot numbers (or 'region counts') very similar, but the heliospheric magnetic field back then behaved very similarly to what we observe today, as seen in Figure 4.
In summary it is probably too soon to panic. In the modern era (Figure 1) there is no precedent for such a protracted activity minimum, but there are historical records from a century ago of a similar pattern. We do expect activity to pick up fairly suddenly soon. In the meanwhile this is a good opportunity to use the excellent new data available from many satellites and ground-based observatories without interference from new flux emergence. We can hope to learn a great deal about how low-level activity works in the network and in the polar caps.

Croissant energetici dal sole

L'altro giorno la NASA ha presentato i primi risultati della missione STEREO, costituita da due satelliti collocati in orbita nei punti lagrangiani L4 e L5 per osservare il sole in modalità stereoscopica. I due occhi satellitari hanno generato immagini e prospettive tridimensionali che hanno finalmente dato una forma a eventi dirompenti come le eiezioni di massa coronale, grosse bolle di plasma solare che colpiscono il campo magnetico terrestre e provocano forti perturbazioni (anche alla propagazione dei segnali radio). Ed è saltato fuori che queste eiezioni assomigliano... a un croissant. Inteso come cornetto del bar. Sembra un risultato banale ma non lo è del tutto perché la forma a mezza luna si spiega con l'effetto distorcente provocato dai campi magnetici solari e sarebbe supportato dalle attuali teorie. Potete visualizzare una ricostruzione animata dell'esplosione legata a un CME in questo filmato QuickTime. A questo altro indirizzo trovate invece la trascrizione di una intervista a uno degli scienziati della missione STEREO e all'audio registrato.

NASA SPACECRAFT SHOW THREE DIMENSIONAL ANATOMY OF A SOLAR STORM

WASHINGTON -- Twin NASA spacecraft have provided scientists with their first view of the speed, trajectory, and three-dimensional shape of powerful explosions from the sun known as coronal mass ejections, or CMEs. This new capability will dramatically enhance scientists' ability to predict if and how these solar tsunamis could affect Earth.
When directed toward our planet, these ejections can be breathtakingly beautiful and yet potentially cause damaging effects worldwide. The brightly colored phenomena known as auroras -- more commonly called Northern or Southern Lights -- are examples of Earth's upper atmosphere harmlessly being disturbed by a CME. However, ejections can produce a form of solar cosmic rays that can be hazardous to spacecraft, astronauts and technology on Earth.
Space weather produces disturbances in electromagnetic fields on Earth that can induce extreme currents in wires, disrupting power lines and causing wide-spread blackouts. These sun storms can interfere with communications between ground controllers and satellites and with airplane pilots flying near Earth's poles. Radio noise from the storm also can disrupt cell phone service. Space weather has been recognized as causing problems with new technology since the invention of the telegraph in the 19th century.
NASA's twin Solar Terrestrial Relations Observatory, or STEREO, spacecraft are providing the unique scientific tool to study these ejections as never before. Launched in October 2006, STEREO's nearly identical observatories can make simultaneous observations of these ejections of plasma and magnetic energy that originate from the sun's outer atmosphere, or corona. The spacecraft are stationed at different vantage points. One leads Earth in its orbit around the sun, while the other trails the planet.
Using three-dimensional observations, solar physicists can examine a CME's structure, velocity, mass, and direction in the corona while tracking it through interplanetary space. These measurements can help determine when a CME will reach Earth and predict how much energy it will deliver to our magnetosphere, which is Earth's protective magnetic shield.
"Before this unique mission, measurements and the subsequent data of a CME observed near the sun had to wait until the ejections arrived at Earth three to seven days later," said Angelos Vourlidas, a solar physicist at the Naval Research Laboratory in Washington. Vourlidas is a project scientist for the Sun Earth Connection Coronal and Heliospheric Investigation, STEREO's key science instrument suite. "Now we can see a CME from the time it leaves the solar surface until it reaches Earth, and we can reconstruct the event in 3D directly from the images."
These ejections carry billions of tons of plasma into space at thousands of miles per hour. This plasma, which carries with it some of the magnetic field from the corona, can create a large, moving disturbance in space that produces a shock wave. The wave can accelerate some of the surrounding particles to high energies that can produce a form of solar cosmic rays. This process also can create disruptive space weather during and following the CME's interaction with Earth's magnetosphere and upper atmosphere.
"The new vantage point of these spacecraft has revolutionized the study of solar physics," said Madhulika Guhathakurta, STEREO program scientist at NASA Headquarters in Washington. "We can better determine the impact of CME effects on Earth because of our new ability to observe in 3D."
STEREO is part of NASA's Solar Terrestrial Probes Program in NASA's Science Mission Directorate in Washington. The program seeks to understand the fundamental physical processes of the space environment from the sun to Earth and other planets.
The Solar Terrestrial Probes Program also seeks to understand how society, technological systems and the habitability of planets are affected by solar processes. This information may lead to a better ability to predict extreme and dynamic conditions in space, and the development of new technologies to increase safety and productivity of human and robotic space exploration.
For more information about NASA's STEREO mission, visit: http://www.nasa.gov/stereo

***

The Surprising Shape of Solar Storms
04.14.2009

April 14, 2009: This just in: The Sun is blasting the solar system with croissants.

Researchers studying data from NASA's twin STEREO probes have found that ferocious solar storms called CMEs (coronal mass ejections) are shaped like a French pastry. The elegance and simplicity of the new "croissant model" is expected to dramatically improve forecasts of severe space weather.
"We believe we can now predict when a CME will hit Earth with only 3-hours of uncertainty," says Angelos Vourlidas of the Naval Research Lab, who helped develop the model. "That's a four-fold improvement over older methods."
Coronal mass ejections are billion-ton clouds of hot magnetized gas that explode away from the sun at speeds topping a million mph. Sometimes the clouds make a beeline for Earth and when they hit they can cause geomagnetic storms, satellite outages, auroras, and power blackouts. The ability to predict the speed and trajectory of a CME is key to space weather forecasting.
"This is an important advance," says Lika Guhathakurta, STEREO program scientist at NASA headquarters in Washington DC. "From a distance, CMEs appear to be a complicated and varied population. What we have discovered is that they are not so varied after all. Almost all of the 40-plus CMEs we have studied so far with STEREO have a common shape--akin to a croissant."
Thousands of CMEs have been observed by NASA and European Space Agency spacecraft, but until now their common shape was unknown. That's because in the past observations were made from only a single point of view. The STEREO mission has the advantage of numbers. It consists of two probes that flank the sun and photograph explosions from opposite sides. STEREO's sensitive wide-field cameras can track CMEs over a wider area of sky than any other spacecraft, following the progress of the storm all the way from the sun to the orbit of Earth.
"STEREO has done what no previous mission could," notes Guhathakurta.
Vourlidas says he is not surprised that CMEs resemble French pastries. "I have suspected this all along. The croissant shape is a natural result of twisted magnetic fields on the sun and is predicted by a majority of theoretical models."
He offers the following analogy: Take a length of rope and hold one end in each hand. Start twisting the ends in opposite directions. Twist, twist and continue twisting until the middle of the rope is a fat knotted mess. "That's how CMEs get started—as twisted ropes of solar magnetism. When the energy in the twist reaches some threshold, there is an explosion which expels the CME away from the sun. It looks like a croissant because the twisted ropes are fat in the middle and thin on the ends."
The shape alone, however, does not tell the full story of a CME. The contents of the CME must be considered, too. How much plasma does it contain? What is the orientation and strength of its internal magnetic field? When a CME strikes, the havoc it causes will depend on the answers—answers the croissant model does not yet provide.
"There is more work to do. We must learn to look at a CME and not only trace its shape, but also inventory in contents," says Guhathakurta. "We are halfway there."
Eventually, the quest to learn what lies inside the croissant will be taken up by other spacecraft such as the Solar Dynamics Observatory, slated to launch in August 2009, and Solar Probe+, a daring mission (still on the drawing board) to fly close to the sun and actually enter these storms near their source.
STEREO isn't finished, though. The two probes are continuing their journeys to opposite sides of the sun for a 24/7, 360-degree view of the star. Along the way, they'll actually run into a few CMEs and have the chance to sample the 'croissants' in situ.

W2A: radio, tv e servizi interattivi dal cielo in S-Band

Il 4 aprile scorso la joint venture tra Ses-Astra e Eutelsat, Solaris Mobile, ha lanciato con successo il nuovo satellite W2A (costruito da Thales Alenia Space), destinato a operare nella S-Band e a distribuire una estesa gamma di servizi radiotelevisivi, telefonici e interattivi. Tutto via satellite, tutto verso dispositivi palmari. Secondo Solaris Mobile si apre una nuova era, anche per servizi che finora non hanno incontrato successo di pubblico (leggi, mobile tv) o successo economico (leggi radio digitale satellitare). Per leggere il comunicato stampa Solaris cliccate qui.
Il giorno successivo nel dare la notizia il Financial Times osservava che la posta in gioco potrebbe essere interessante, specie se il satellite saprà essere una alternativa percorribile da vecchi e nuovi entranti in mercati ormai saturi come quello della telefonia mobile. Anche dal punto di vista regolamentare le frequenze della S-Band (tra i 2 e i 2.4 GHz) fanno notizia, almeno in Europa, dove secondo lo stesso quotidiano la Commissione starebbe per dare il via libera a una mega-licenza su scala continentale, favorendo due operatori "locali" (come Solaris Mobile e Inmarsat www.inmarsat.com) a detrimento dei due americani ICO Global e TerreStar. La licenza, afferma FT, consentirebbe di erogare servizi dal cielo in 27 nazioni. La European Satellite Operators Association ha realizzato una interessante brochure dedicato proprio alla regolamentazione dello spettro satellitare, che per evidenti ragioni, richiede più di altri un approccio davvero internazionale.

Tornando al lancio di W2A e alle future prospettive di servizi multimediali convergenti per utenti mobili, non è facile sbilanciarsi in previsioni dopo le esperienze (alterne) finora accumulate dalla radio digitale negli Usa o dai diversi servizi di accesso satellitare a Internet. Il fattore nuovo, nell'equazione proposta da Solaris Mobile, è la versatilità di questo nuovo veicolo e del suo payload multifunzionale. Dall'alto potranno arrivare servizi radio, televisivi, di navigazione... Tutte cose interessanti, almeno sulla carta, proposti da un gruppo forse più solido finanziariamente rispetto a Sirius XM. Vedremo come finirà, anche sulla scorta delle decisioni prese dalla Commissione sul piano delle licenze.

European groups set to win S-band radio rights

By Maija Palmer in London April 5 2009 20:15

Two European satellite companies are this week set to be awarded rights to a band of radio spectrum that could be used to create new Europe-wide mobile phone services.
Inmarsat, the UK-based satellite operator, and Solaris Mobile, a joint venture between Luxembourg-based SES Astra and Eutelsat of France, are expected to be given 18-year rights to S-band radio spectrum in 27 countries across Europe. The decision will leave the two US bidders, ICO Global Communications and TerreStar, disappointed.
The S-band licence is potentially very valuable. The European Commission has chosen to pool the S-band licences from all its member states, and award them in one block. Usually, bands of spectrum are awarded or auctioned on a country-by-country basis.
Mobile phone operators, such as Vodafone, have therefore had to spend years gathering licences for pan-European mobile phone coverage. The S-band spectrum has been earmarked specifically for satellite companies, and the European Commission has indicated it would like the spectrum to be used to develop services such as mobile television.
Steve Maine, chief executive of Solaris, said the company was considering new services, including mobile television, mobile radio, information delivery such as traffic data to cars, and communications systems for the emergency services.
But analysts believe the real value could come from satellite companies partnering with terrestrial mobile phone operators wanting to use the spectrum.
The S-band is quite close in frequency to third-generation mobile phone spectrum and could be used for mobile data. Existing 3G equipment, such as mobile handsets and masts, could be reconfigured to work with S-band. For mobile phone operators wanting more bandwidth for broadband services across Europe, this could be a good way in.
The S-band spectrum could also be used by a new entrant into the mobile phone market, for example, if Google wanted to build mobile broadband services across Europe. Google has invested in a company building satellite broadband coverage in Africa and has been active in building Wimax mobile broadband networks in the US. Whether a company such as this will step up for a partnership is still unclear.

I retroscena della collisione spaziale

Tra i primi a dare la notizia della collisione spaziale tra il satellite numero 33 (lanciato nel 1997) della costellazione Iridium e un non meglio precisato satellite non-operativo russo (lanciato nel 1993) - avvenuta nella cosiddetta junk orbit, l'orbita spazzatura, a circa 800 km di quota - c'era il 60-seconds Science Blog di Scientific American (grazie a Renato per la segnalazione). Iridium ha una storia molto travagliata, dal primo progetto covato in casa Motorola, al lancio del servizio nel 1998, dalla chiusura per fallimento nel 1999, alla ripresa nel 2001, da parte di un gruppo di investitori privati che sostengono di avere poco meno di 300 mila abbonati. Iridium continua a offrire servizi di telefonia in voce e dati, secondo Wikipedia è vitale per le comunicazioni con le basi scientifiche antartiche.
Per ulteriori approfondimenti sul problema delle collisioni orbitali e dei detriti spaziali potete consultare le newsletter del NASA Orbital Debris Program Office. Non ho capito bene perché, forse per i contatti con la Russia, più probabilmente per la forte attenzione nei confronti del programma spaziale di Pechino, ma l'agenzia cinese Xinhua offre un coverage dettagliatissimo sulla vicenda, raccogliendo dichiarazioni di molte fonti interessanti. Tutti i lanci sono raccolti in questa pagina, che vi suggerisco di consultare subito. Fonti americane, russe e delle Nazioni Unite (attraverso il United Nations Office for Outer Space Affairs) hanno invocato misure e regolamentazioni destinate a evitare in futuro questi incidenti, che oltre a recare danno a infrastrutture spaziali operative possono liberare in orbita pericolosi detriti radioattivi provenienti dai satelliti ad alimentazione nucleare. Lo statement ufficiale di Iridium lo trovate qui. Il 22 febbraio dovrebbe partire una nuova missione Shuttle ma non si prevedono rischi legati a questo inatteso incidente.

Feb 11, 2009 06:15 PM
Space crash: Commercial and Russian satellites collide in orbit
By John Matson in 60-Second Science Blog

A commercial satellite collided with a Russian satellite over Siberia yesterday, yielding a cloud of fragments, according to a NASA scientist tracking space debris. The collision between the commercial satellite, belonging to the American communications firm Iridium, and the Russian satellite, believed to be defunct based on its advanced age, was the first of its kind, says Nicholas Johnson, chief scientist at the NASA Orbital Debris Program at Johnson Space Center in Houston. (A spokesperson for Iridium said a statement on the incident would be released shortly.)
"In the past almost 20 years, there have been three other accidental collisions between objects in orbit, but they've all been very minor," Johnson says. "The most debris ever produced in an event was like four debris, and this is two intact spacecraft colliding, and we have hundreds of debris out there. We don't know exactly how many yet."
According to Johnson, the military sky-watchers who track satellites in orbit picked up the collision 490 miles (790 kilometers) above Earth Tuesday. "One of the things that they discovered yesterday afternoon ... was all of a sudden, where two satellites used to be, there were two clouds of debris," he says. The actual crash appears to have occurred just minutes before noon, Eastern Standard Time.
Johnson says NASA has already determined that the debris cloud poses "no significant new risk to the International Space Station." The next space shuttle mission, which may launch as early as February 22, should be in the clear as well, according to the space agency.
Such a collision between two intact spacecraft may be unprecedented, but it is not completely unexpected. "There are no rules of the road in space," Johnson says. "Anybody can fly anywhere they want." Even concerted efforts to track and guide spacecraft in orbit are subject to some uncertainty in trajectory estimates. At seven miles (11 kilometers) per second, Johnson says, "a little error means a lot."

La ionosfera si abbassa

Ho letto solo oggi, con qualche settimana di ritardo una notizia che riguarda i primi risultati ottenuti da un satellite lanciato lo scorso aprile per studiare la ionosfera e i suoi fenomeni. Il satellite CNOF/S, Communication/Navigation Outage Forecast System, fa parte di una missione dell'Air Force americana con la collaborazione di NASA e università il cui obiettivo è fornire dati sulle possibili alterazioni nelle comunicazioni alle alte frequenze, in virtù di fenomeni perturbativi come le "scintillazioni", che disturbano le operazioni terra-satellite anche nelle UHF e in banda L.

Secondo le ultime analisi effettuate con gli strumenti della missione CINDI, Coupled Ion-Neutral Dynamics Investigations (qui trovate delle interessanti animazioni), la ionosfera si starebbe abbassando di quota. La regione di transizione tra ionosfera e spazio, teoricamente collocata intorno a quota 950 chilometri durante il giorno è stata misurata a 800 chilometri. Nelle ore notturne il limite si dimezza, scendendo a 420 chilometri di quota contro i 640 misurati da terra.
I due articoli che seguono, ricavati dal sito Space Mart e dal sito della University of Texas Dallas (cui è affidata la direzione scientifica della missione CINDI) riassumono questo e altri risultati, tra cui per esempio il rilevamento di un livello termico ionosferico assai più basso del previsto. La ionosfera è più fredda e meno alta. In teoria, una quota più bassa implicherebbe una riduzione dei percorsi propagativi per chi ascolta in onde medie e corte. Ma in realtà sospetto che i dati raccolti in questi mesi dalla missione C/NOFS-CINDI siano piuttosto uno strumento di conoscenza aggiuntivo, più preciso di quelli, molto circoscritti e limitati, di cui disponevamo finora. Il ritratto della ionosfera che sta emergendo non è "diverso", ma "nuovo". Il che non lo rende meno interessante per noi.

Contraction Of Boundary Between The Earth's Ionosphere And Space

The C/NOFS mission gives scientists a new tool for forecasting space weather. The CINDI instrument aboard C/NOFS specifically studies the major elements that influence space weather near Earths equator.

by Staff Writers (Credit: NASA) Washington DC (SPX) Dec 19, 2008

Observations made by NASA instruments onboard an Air Force satellite have shown that the boundary between the Earth's upper atmosphere and space has moved to extraordinarily low altitudes. These observations were made by the Coupled Ion Neutral Dynamics Investigation (CINDI) instrument suite, which was launched aboard the U.S. Air Force's Communication/Navigation Outage Forecast System (C/NOFS) satellite on April 16, 2008.
The CINDI suite, which was built under the direction Principal Investigator Rod Heelis of the University of Texas at Dallas, includes both ion and neutral sensors and makes measurements of the variations in neutral and ion densities and drifts.
CINDI and C/NOFS were designed to study disturbances in Earth's ionosphere that can result in a disruption of navigation and communication signals. The ionosphere is a gaseous envelope of electrically charged particles that surrounds our planet and it is important because Radar, radio waves, and global positioning system signals can be disrupted by ionospheric disturbances.
CINDI's first discovery was, however, that the ionosphere was not where it had been expected to be. During the first months of CINDI operations the transition between the ionosphere and space was found to be at about 260 miles (420 km) altitude during the nighttime, barely rising above 500 miles (800 km) during the day.
These altitudes were extraordinarily low compared with the more typical values of 400 miles (640 km) during the nighttime and 600 miles (960 km) during the day.
The height of the ionosphere/space transition is controlled in part by the amount of extreme ultraviolet energy emitted by the Sun and a somewhat contracted ionosphere could have been expected because C/NOFS was launched during a minimum in the 11-year cycle of solar activity. However, the size of the actual contraction caught investigators by surprise.
In fact, when they looked back over records of solar activity, they found that C/NOFS had been launched during the quietest solar minimum since the space age began.
This extraordinary circumstance is providing an unparalleled opportunity to study the connection between the interior dynamics of the Sun and the response of the Earth's space environment.
CINDI is a NASA sponsored Mission of Opportunity conducted by the University of Texas at Dallas. NASA's Explorer Program at Goddard Space Flight Center, Greenbelt, Md., managed the CINDI mission. The Explorer Program provides frequent flight opportunities for world-class scientific investigations from space within heliophysics and astrophysics.
The CINDI investigation is carried out as an enhancement to the science objectives of the C/NOFS satellite undertaken by the Air Force Research Laboratory and the Space and Missile Command Test and Evaluation Directorate.

***

UT Dallas Project Helps Fill Out Picture of Earth’s Ionosphere

Researchers’ Instruments Reveal Surprises About Size and Shape of Electrically Charged Layer

Dec. 16, 2008

A space weather satellite with Coupled Ion-Neutral Dynamics Investigation (CINDI) instruments aboard have for the first time revealed the size and shape of the gaseous envelope of electrically charged particles that surrounds the globe.

Called the ionosphere, this essential border between Earth and space has now been mapped at its upper boundary and shown to occupy less height than expected.
Measurements from CINDI instrumentation have made the first map of the ionosphere’s upper surface. It expands and contracts from day to night but has much less height than expected.
A collaboration among NASA, the U.S. Air Force Research Laboratory (AFRL) and the University of Texas at Dallas, CINDI is revealing what happens during periods of low sunspot activity, when the upper atmosphere cools off.
The ionosphere plays a particularly important role in satellite communication and any type of technology that uses space-based communications. GPS systems used by ships, trucking companies, and airplanes depend on reliable, uninterrupted streams of information from satellites, which must punch a signal cleanly through the ionosphere.
“Any radio or location system signal that utilizes space-based communication has to go through the ionosphere,” said CINDI Principal Investigator Rod Heelis, director of the Hanson Center for Space Sciences at UT Dallas. “On its best day, the ionosphere just bends that signal rather like water bends light. On its worst day it can completely distort that signal so that it doesn’t make it out the other side.”
Predicting when these disturbances might occur is a key goal of the CINDI project and its satellite, the Communication/Navigation Outage Forecast System (C/NOFS).

CINDI reveals for the first time:

• A view of the ionosphere never seen before, during solar “quiet” times.
• A map showing the size and shape of the Earth’s ionosphere.
• That the ionosphere is up to 100 degrees cooler than previously thought.
• That the effective thickness of the ionospheric shell is less than expected.
• A link between the extent of the ionosphere and solar activity levels observed at solar minimum.
• A view of the daily expansion and contraction of the ionosphere around the equator.
  

“The ionosphere is extremely cold at night, leading to a much thinner altitude and less dense layer than we expected,” Heelis said. “We have found that it is up to 100 degrees cooler than we expected and the effective thickness of the ionospheric shell is smaller than we expected.”
Heelis said CINDI revealed that the ionosphere expands during the day, when the upper surface rises, but not as high as the team thought it might. Further, the daily expansion and contraction of the ionosphere has been observed continuously around the equator for the first time. Had sunspot activity not dropped off—with associated cooling of the ionosphere—scientists would not have been able to watch the ionosphere expand and contract.
The so-called “quiet time” view of the ionosphere, when sunspot activity is low, allows Heelis and Greg Earle, another UT Dallas physics professor and CINIDI team member, to study the region of the ionosphere that is hazardous to radio communications.

Heelis and Earle built the two instruments that comprise CINDI:

The Ion Velocity Meter, which measures the direction and speed of ions as well as their density, temperature and chemical composition.

The Neutral Wind Meter, which measures the speed and direction of the neutral atoms and molecules in the near vacuum of space.

The 20-pound package of sensors and electronic equipment was fabricated in Heelis’ UT Dallas laboratory with Earle’s assistance and in collaboration with Paul Mahaffey of NASA’s Goddard Space Flight Center.

CINDI was carried on the C/NOFS satellite that was launched on April 16, 2008 on a Pegasus XL rocket aboard Orbital Science Corporation’s L-1011 “Stargazer” jet. The C/NOFS mission was launched to explore ways to forecast disturbances in the Earth’s ionosphere that can result in a disruption of navigation and communication signals.
“Years ago, my basic question began as, ‘How does our space environment interact with the sun?’” Heelis said. “I was intellectually curious about that. But now, as we become more dependent on assets in space, answering that question has real importance to everyday commerce, to military and commercial communications and navigation. NASA and the Air Force want to know the answers, and it’s enlightening to see major agencies working with us at UT Dallas to share resources and work on these problems together.”
Heelis and representatives from NASA and the Air Force presented the recent results from CINDI at the 2008 fall meeting of the American Geophysical Union.

La missione Cluster "ascolta" la stazione radio aurorale

All'acuto sguardo di Piero Bianucci sulla Stampa non sono sfuggite due notizie dell'ESA sulle missioni Cluster e SOHO. Partiamo dal secondo caso, simpatico ma un po' marginale per i nostri interessi. La missione SOHO, un osservatorio orbitale dedicato al geomagnetismo e all'attività solare, ha stabilito un record con ben 1.500 nuove comete registrate. Il fatto di inquadrare spesso il nostro astro lo pone in una posizione avvantaggiata rispetto agli osservatori terrestri, che tuttavia sono i veri fautori di questa caccia al pezzo di ghiaccio con la coda: sono loro che esaminando le immagini trasmesse da SOHO ogni 15 minuti si accorgono di quei puntini in movimento.
Le notizie che arrivano da Cluster sono invece molto più pertinenti ai nostri interessi propagativi, anche se a ben considerare le ultime scoperte torneranno utili a chi i segnali radio li vuole ascoltare dai pianeti lontani. La missione costitituita da quattro satelliti disposti in un particolare array pensato per conferire una cornice referenziale alle osservazioni radio, ha appurato il funzionamento della Auroral Kilometric Radiation, o radiazione aurorale nelle bande chilometriche, una particolare emissione radio originata dal nostro pianeta nel cono ionosferico sopra i poli, la regione in cui si producono le aurore. E' un emissione formata da una miriade di fonti che "sparano" in una zona dello spettro compresa tra i 50 e i 500 kHz. Cluster ha consentito di stabilire un nuovo modello per la modalità e la polarizzazione del segnale, che invece di essere banalmente a forma di cono svuotato come proposto una trentina d'anni fa, risponderebbero a una teoria più recente più simile a quanto riscontrato nelle magnetosfere di altri pianeti e cioè a un segnale orientato su un piano tangente all'area di ionizzazione da cui parte l'emissione. Questo può aiutare molto i radioastronomi impegnati nella ricerca sulle magnetosfere non terrestri e su eventuali segnali di vita intelligente. Il sito dell'ESA riporta alcuni file ottenuti convertendo in frequenze audio il variabile spettro del segnale AKR misurato con lo strumento WBD appositamente costruito dall'Università dello Iowa, un ricevitore di campi elettrici e magnetici a frequenza comprese tra 25 Hz e 577 kHz (in pratica un ricevitore spaziale di radiofari e frequenze naturali). Davvero eccezionale.

Beamed radio emission from Earth

27 Jun 2008

A recent study reveals how the most powerful emission of terrestrial origin, the Auroral Kilometric Radiation (AKR), is beamed into space. This result was obtained using data collected by the four satellites of the Cluster mission. These new data were found to be inconsistent with two leading AKR beaming theories developed 30 years ago, but support a more recent one. The result has important implications for radio studies of planetary magnetospheres, including radio searches for exo-planets.

Seen from deep space, the Earth is a powerful planetary radio source, comparable to Jupiter, with maximum output power in the 50-500 kHz range. At such frequencies, the dominant emission is Auroral Kilometric Radiation (AKR), a natural electromagnetic wave generated in the auroral zones. (An auroral zone is an annular ring around each magnetic pole where auroras are most likely to occur, see Figure 1.)
AKRs are intimately linked with auroras, or more precisely with the energetic electron beams that cause the auroras. (As a reminder: it is the precipitation of such beams and their interactions with oxygen and nitrogen atoms which illuminate the sky at an altitude of about 100 km.)
Satellite observations since the 1970's have greatly enhanced our knowledge of AKR. In particular, these observations have enabled us to pin down the physical process generating this powerful emission. But even 40 years after its discovery, a fundamental problem remains: in which direction is AKR beamed with respect to the Earth's magnetic field?

Open question: How is AKR beamed in relation to Earth's magnetic field?

The question is actually more complicated than it sounds. As revealed by high-time resolution data, AKR is in fact composed of many elementary radiation sources (follow the link on the right-hand menu to listen to the sound of AKR). So far, scientists have modelled the angular beaming characteristics of AKR in a statistical sense, mainly using data collected by a single satellite. As a result, a few beaming theories have been proposed but the only way to discriminate between them is to directly measure the angular beaming pattern of individual AKR bursts. This is what has been recently achieved thanks to data collected by the ESA/NASA Cluster mission.
The Cluster constellation consists of four satellites, each equipped with the same type of sensitive radio wave receiver - the WideBanD (WBD), built by the University of Iowa, USA, and financed by NASA. By flying in formation above AKR sources, this space fleet provides scientists with a unique opportunity to determine the angular power pattern of individual AKR bursts.
First of all, the WBD system records waves with sufficient time and frequency resolution to isolate emission from individual elementary AKR sources.
In addition, since the Cluster constellation forms a 2-dimensional array in the sky, it can simultaneously sample the burst from different viewpoints.
Finally, by measuring the differential delays between all pairs of spacecraft (6 combinations in total), the locations of individual AKR bursts can also be determined (Mutel et al., 2003). This provides a spatial filter, which isolates radiation from a single region and allows the array to sample individual burst power patterns.

Cluster data compatible with recent model; rules out older ones

In a recent study, Dr. Robert Mutel (University of Iowa) and colleagues report the analysis of more than 12 000 individual AKR bursts collected by the Cluster mission (see Figure 3). "Thanks to Cluster, we could demonstrate that individual AKR bursts do not radiate in the manner described by two models that were proposed some 30 years ago. However, these new data do back up the numerical model developed 10 years ago by Louarn and Le Quéau", says Mutel, lead author of this discovery which is reported in Geophysical Research Letters on 09 April 2008.
"AKR is similar to radio emissions that emanate from other magnetospheres at Jupiter, Saturn, Uranus and Neptune but also certain solar and stellar radio bursts. The radio emission is a result of a plasma instability that frequently develops in astrophysical magnetospheres which can efficiently convert free energy present in energetic particles into radiating electromagnetic waves. Its full comprehension is therefore of crucial importance", wrote Philippe Louarn (CNRS, Toulouse, France) in a recent review on the subject.
The new result clarifies how the radiation is beamed, which is in a narrow plane tangent to the magnetic field at the source, rather than a hollow cone as previously suggested.
"This has important implications for the study of AKR from other planets, stellar magnetospheres, and even the search for exo-planets by radio telescopes", notes Melvyn Goldstein, NASA Cluster project scientist.
"This result is a major scientific breakthrough obtained by the Cluster mission", says Philippe Escoubet, Cluster project scientist at the European Space Agency.

Related publications

Mutel, R. L., Christopher, I. W., & Pickett, J. S., "Cluster multi-spacecraft determination of AKR angular beaming", Geophys. Res. Lett., 35, L07104, 2008, doi: 10.1029/2008GL033377.

Louarn, P., "Generation of auroral kilometric radiation in bounded source regions", Lect. Notes Phys, 687, 55-86, 2006, doi: 10.1007/3-540-33203-0_3

Louarn, P., & Le Quéau, D., "Generation of the auroral kilometric radiation in plasma cavities-II. The cyclotron maser instability in small size sources", Planet. Space Sci., 44, 211– 224, 1996, doi: 10.1016/0032-0633(95)00122-0

Mutel, R. L., Gurnett, D. A., Christopher, I. W., Pickett, J. S., & Schlax, M., "Locations of auroral kilometric radiation bursts inferred from multispacecraft wideband Cluster VLBI observations: 1. Description of technique and initial results", J. Geophys. Res., 108(A11), 1398, 2003, doi: 10.1029/2003JA010011.