Le informazioni meteomarine sfidano il tempo viaggiando via radio

Almeno per quanto mi riguarda (e avrete capito quanto riesca a essere nostalgico davanti a una radio) continua a esercitare il suo misterioso fascino la ricezione dei servizi di "radio facsimile" che ancora oggi utilizzano le frequenze tra 2 e 25 MHz per inviare informazioni meteorologiche di tipo visuale. Cartine, previsioni del tempo, correnti e onde marine, altezza dei ghiacci, immagini riprese dai satelliti... Informazioni rivolte soprattutto ai naviganti e ai velisti meno attrezzati dal punto di vista delle comunicazioni satellitari e per quelli che allontanandosi troppo dalle coste non possono attaccarsi a Internet via cellulare per il loro fai-da-te meteorologico. Un sistema abbastanza economico, per chi trasmette e per chi riceve, tanto da essere giudicato dagli addetti ai lavori ancora molto utile. Quando la Guardia Costiera americana aveva minacciato di tagliare le spese per la distribuzione via radio delle sue informazioni le proteste inviate da navigatori da diporto e piccoli professionisti del mare sono bastate per tenere ancora in vita il servizio, che per adesso prosegue. Nella stessa mattina ho ricevuto, senza riuscire a identificarle pienamente, immagini da stazioni nel nord ovest del Canada e dell'Alaska.

E' soprattutto un sistema completamente analogico, rimasto immutato dai tempi delle prime "telefoto" di parecchi decenni fa: l'immagine viene applicata su un rullo ruotante e un pennino luminoso analizza riga per riga i livelli di nero. Questo dato viene convertito in un segnale elettrico che varia continuamente nel tempo (la definizione stessa di analogico) e a sua volta il segnale va a modulare in frequenza una portante: a variazione di luce corrisponde una variazione lineare di frequenza.L'unico elemento di novità oggi à il software che finge di essere un sistema di ricezione basato su un identico rullo ruotante alla identica velocità e su un pennino che invece di esplorare una foto disegna l'immagine ricevuta con l'inchiostro. L'effetto, sullo schermo del pc, è lo stesso. Come in una Polaroid dipinta a mano, la cartina meteorologica si forma anch'essa riga dopo riga, con una lentezza d'altri tempi. A seconda delle dimensioni della mappa ci vuole almeno un quarto d'ora per trasmettere e ricevere una immagine completa. Questa che vedete è una

fotografia satellitare all'infrarosso della zona sud-occidentale del Pacifico (si intuisce la cima nord della Nuova Zelanda) e l'ho ricevuta questa mattina, alle nostre 9, dalla stazione meteorologica NOAA di Honolulu nelle Hawaii. La frequenza è di 11.090 kHz, che per il

radiofax corrisponde in genere alla massima frequenza di deviazione rispetto a una portante che per convenzione è fissato 1900 Hz più in basso: è qui che bisogna quindi sintonizzare il ricevitore se si ascolta in banda laterale unica (ci sono ricevitori professionali che applicano uno shift automatico di 1900 rispetto a una lettura nominale ma non è il mio caso).

Il software utilizzato per la decodifica è il solito CocoaModem per Macintosh, che è in grado di riconoscere altre modalità di trasmissione dati analogiche e digitali. La qualità della ricezione è sorprendentemente buona per tutta questa distanza. Potete divertirvi a confrontare la foto ricevuta via radio (il trasmettitore ha 4 kW) con questa distribuita dalla NOAA via Internet- Tutto sommato la leggibilità mi sembra accettabile:

Non esistono molte risorse Web che elencano i servizi radiofax oggi disponibili con orari e frequenze, ma un paio di indirizzi possono bastare. Uno è quello della lista curata dalla Guardia Costiera USA, l'altro è la pagina sul facsimile HF allestita da William Hepburn sul suo DX Info Centre. Quest'ultimo riporta ancora servizi che non esistono più, come quello un tempo trasmesso da Roma Radio, ma è abbastanza attendibile.

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.

La meteorologia viaggia sui canali data del satradio

Questa interessante storia della NASA parla di alcune avanzate applicazioni meterologiche che sono state trasformate, grazie alla collaborazione con alcune società commerciali, in altrettanti servizi di previsione del tempo a brevissimo termine distribuiti attraverso i canali dati dei satelliti di radio digitale ex-XM Radio. Secondo l'articolo ci sarebbero già diverse decine di migliaia di abbonati tra i numerosi proprietari di barche da diporto e pesca che solcano le non facili acque intorno ala Florida, un'area dove i mutamenti atmosferici possono essere tanto repentini quanto devastanti. XM Radio ha una sua divisione specializzata in servizi meteo raggiungibile sul sito XMWXweather. Tra i fornitori dei servizi avanzati di cui parla la NASA - i dati sono basati sui dati forniti dallo Short-term Prediction Research and Transition Center (SPoRT) - ci sono società come WorldWinds Inc e WxWork. I dati SPoRT sono disponibili gratuitamente anche via Web, all'indirizzo già riportato. In questo caso i canali XM trasporano gli overlay di informazioni sul tempo elaborate e aggiornate in tempo reale. I dati viaggiano via satellite e finiscono sui navigatori di bordo dei natanti, dove vengono combinati con mappe digitali e posizionamento GPS. WxWorks per la ricezione e la decodifica delle informazioni ha anche realizzato, con la collaborazione di un produttore di antenne di bordo chiamato Digital Antenna, un apposito ricevitore XM Radio. I servizi vengono proposti anche per la navigazione aerea e land based.
Eccco una applicazione interessante per una piattafoma satellitare come Sirius XM . Peccato che questa nicchia di prodotto non abbia ancora, evidentemente, un grande impatto sul mercato.

NASA's Gift to Mr. Claus
12.24.2008

Terry Claus, captain of a 53-foot charter boat called The Qualifier, received something that helped him avoid a disaster at sea--namely, data transmitted onto his GPS screen. If "data" isn't your idea of a Christmas gift, just listen:

"One night, my wife, children, and I were fishing for swordfish 25 miles off the Miami coast," says Claus. "We saw black clouds to the west. That's not unusual where we live. Florida storms sometimes build over land and then dissipate. But that night, when I checked the radar on my GPS, I saw an incredible line of severe thunderstorms moving towards us -- and fast."

"I checked the lightning strike screen, and it looked like a chained link fence of continuous lightning," he continues. "I shouted, 'Reel in the lines! We have to get out of here fast!' I could see on the screen where the cloud mass was weakest, so I followed that route. A 747 jet flew overhead and seemed to be following the same route we were following. We must have been looking at the same data! We made it to port safely."
NASA's SPoRT program (short for Short-term Prediction Research and Transition) at the Marshall Space Flight Center, helped make Claus's bird's eye view of the weather possible that night.
The SPoRT team assists a small company called WorldWinds, Inc. in Slidell, Louisiana in making some premiere products available to the marine community. NASA supplies WorldWinds with high resolution satellite data on ocean and atmospheric conditions. WorldWinds repackages the data, along with other weather/data products they generate themselves and some radar data from WxWorx, for the mariners along the Gulf and Atlantic coasts. About ten thousand of them subscribe to the data service via XM satellite radio.
Any time they feel a little edgy about what the day, or night, might hold in store, Claus and other boaters can scrutinize a GPS for answers. With the push of a button, a boat captain can choose from among views of sea surface temperatures, Doppler radar, wind speed, wind direction, lightning strikes, and more, both real-time and forecasted.
"Our job is to help businesses and other government agencies find vital ways to use our data," says Dr. Gary Jedlovec, satellite meteorologist and SPoRT principal investigator. "In fact, weather forecasters all over the US, including coastal regions of Florida, use many of our data products to improve forecasts. Accurate marine weather forecasts are especially crucial to boaters. They sure don't want to be surprised by high winds, 10-foot waves, and lightning strikes."
Sea surface temperatures can be a significant factor in spawning the storms Claus dreads. Sea surface temperatures also play an important role in creating just the right setting for something Claus loves – a lot of fish in one place. Each species of game fish has a range of water temperature they prefer, so "SST charts" can lead a fisherman to his prize catch.
There's another thing that helps create the perfect ambience for a fish party – plankton. The green stuff is almost always the most popular hors d'oeuvre. If an ocean area has a lot of plankton, it's a likely gathering spot. The SPoRT team knows how to use NASA satellite data to find such areas. High chlorophyll concentration, indicated in satellite data by greenness (the greener the more chlorophyll), means lots of plankton.
"If you know where blue water [no plankton] meets green [more plankton], you'll find more bait fish, and then more catchable fish," says Claus. "Fish swim up and down the edge of the weed boundaries and also the defined edge where warmer water meets cooler water."
That's why WorldWinds uses the SPoRT sea surface temperature data along with SPoRT chlorophyll data as components in a fishing product called FishBytes that reveals when and where the impromptu fish parties take place. Like the weather data, this product is available via XM radio on a GPS.
NASA helps fishers find fish feasting. (Say that 10 times rapidly!) And what about the poor fish? It just doesn't seem fair.
"Most of our customers are charter fishing captains," says Benjamin Jelly of WorldWinds. "Environmental and conservation groups concerned for fish view us, and the charter fishers, in a positive light."
"When we take out charter clients, we follow the environmental laws concerning limit numbers and size," explains Claus. "And when we fish in tournaments, we use circular hooks for bait. It's a tournament rule. The fish can't swallow the hook, so the fish aren't hurt. Once we catch a fish, we release it immediately. In fact, an angler's tournament score is based on the number of releases he or she makes."
Many sport fishermen also participate in voluntary tagging programs. This allows researchers, including fisheries biologists and marine scientists, to garner more information about species numbers, migration patterns, and environmental preferences.
"There are many, many tournament participants, and literally thousands of recreational fishermen, some of which fish year-round," says Jelly. "So our system allows more fishermen to apply more tags and collect more data about these species. That's good for the fish."

Amnesia ricorda il futuro

Matteo, il protagonista di Amnésia su Radio2, ha ricordato di avere una barca a vela. E come ogni velista che si rispetti, salendo a bordo si è rimesso all'ascolto del Meteomar, il servizio di previsioni del tempo per la navigazione diffuso tutti i giorni in VHF e in media frequenza dall'Aeronautica militare. Potete ascoltare le divagazioni di Matteo sull'arte di prevedere il tempo e - verso la fine della trasmissione - qualche secondo di audio del Meteomar, sul podcast della puntata di Amnésia di ieri 20 novembre. Nella sezione fotografica del sito del programma trovate delle belle foto di Genova.

Voci dall'uragano

Sto ascoltando la diretta no stop di WWL 870 da New Orleans. Il coverage su Gustav è emozionante. La stazione all news ha allestito un sito speciale, Hurricane Central, per condensarvi tutte le notizie dell'ultimo minuto. Lo stream audio è aperto e sono le 2.50 adesso in Louisiana.

Una curiosa intersezione tra radar e letteratura

Disclaimer: questo post non riguarda la radio. Ripensandoci però non è nemmeno tanto vero, visto che al centro di questo romanzo psicologico di una debuttante giovane autrice americana - medico trasformato in "master of fine arts", cresciuta in Oklahoma da una famiglia ebrea di origini ungheresi - si nasconde una fantascientifica ipotesi di sostituzione di persona attraverso la creazione di "miraggi" mediante radar per ricerche meteorologiche. Una storia tutta giocata in chiave borgesiana che si interroga sulla questione dell'identità e dell'amore. Il radar mi sembra sufficientemente radiofonico da farmi restare on topic.
L'ho trovata ieri recensita sulla Book Review del New York Times e ho anche trovato su Bookslut una bella intervista all'autrice di Atmospheric Disturbances (Perturbazioni atmosferiche) Rivka Gelchen. Della Galchen la rivista superintellettuale The Believer ha pubblicato un saggio dedicato alle ipotesi degli universi multipli legati alle teorie della meccanica quantistica (gulp, anche questo non c'entra molto con la radio, ma nemmeno con la politica quindi spero non vi offendiate come è accaduto in questi giorni a qualcuno).
Visto che ormai sui giornali è tutto un pullulare di suggerimenti per letture da spiaggia, prendetela come un mio personale suggerimento alla cieca. Qualcosa mi dice che verrà tradotto presto anche in Italia.

July 13, 2008
Who Do You Love?
By LIESL SCHILLINGER

ATMOSPHERIC DISTURBANCES By Rivka Glachen. 240 pp. Farrar, Straus & Giroux. $24.

In one of his best-known jokes (anti-joke is closer to it), the unsmiling comedian Steven Wright says, in a monotone: “I woke up one day and everything in the apartment had been stolen and replaced with an exact replica. I said to my roommate, ‘Can you believe this? Everything in the apartment has been stolen and replaced with an exact replica.’ He said, ‘Do I know you?’ ” This existential conundrum — the question of what makes an original different from a copy (and how anyone can prove that he is who he thinks he is once the matter is called into doubt) — is both the springboard and the ensuing spring of “Atmospheric Disturbances,” a brainy, whimsical, emotionally contained first novel by Rivka Galchen, a young M.D. turned M.F.A.
Galchen’s narrator, a fussy 51-year-old psychiatrist named Leo Liebenstein, believes that his beautiful, much-younger Argentine wife, Rema, has been replaced by a “doppelgänger,” a “simulacrum,” an “impostress,” an “ersatz” spouse. “Last December,” Leo explains, “a woman entered my apartment who looked exactly like my wife.” Like his wife, the newcomer has the same “wrinkly boots,” the same Argentine accent with “the halos around the vowels,” the “same baby blue coat with jumbo charcoal buttons, same tucking behind ears of dyed corn silk blond hair. Same bangs cut straight across like on those dolls done up in native costumes that live their whole lives in plastic cases held up by a metal wire around the waist.” The idea that this cockatiel of a woman could not be the Rema in question is absurd, but the evidence of Leo’s eyes and ears doesn’t persuade him. “Same everything, but it wasn’t Rema,” he maintains. “It was just a feeling, that’s how I knew.”
So far, this could be farce, trompe l’oeil, Ionesco, Magritte. But the story quickly changes course. Seeking a logical explanation for the presence of the interloper (it can’t be a case of “Rema-based psychosis,” he conveniently concludes), Leo delves into the research of a quasi-paranormal scientific association called the Royal Academy of Meteorology, in particular the publications of a man named Tzvi Gal-Chen, whose work on Doppler radar, “initial value problems” and “atmospheric modeling” may contain the key to the “real” Rema’s disappearance. Tzvi Gal-Chen has his drawbacks: for one thing, he appears to be dead; for another, the “fake” Rema may be impersonating him; but at least he’s accessible by e-mail. Also, Gal-Chen once presented a scientific paper in Buenos Aires, and Rema was born there. Could these two random occurrences be related? Leo hops a plane to Argentina to find out, using Gal-Chen’s research on retrieving “thermodynamic variables from within deep convective clouds” to guide his own blundering “attempts at retrieval” of the “real” Rema. No, this is not chick lit.
It’s unusual — in fact (why be coy?), it’s extremely rare — to come across a first novel by a woman writer that concerns itself with such quirky, philosophical, didactic explorations; a novel in which the heart and the brain vie for the role of protagonist, and the brain wins. While the voice and mood of the novel are masculine, clinical and objective (Leo registers Rema’s distress with detachment, recording it but not feeling it), the book’s descriptions of colors, smells, clothing and bodies show feminine perception: Rema’s hair has the “smell of grass”; a woman has “wet cement eyes”; a ’70s shirt with a butterfly collar has “pearline” fasteners. This attention to detail doesn’t pass without comment. Rema teases Leo for the attention he pays to clothes, while Leo mocks his mother’s “excessive aesthetic sensitivity” even as he tries to dictate the color, fabric and buttons of a new coat for a Rema clone in Patagonia.
Galchen’s inventive narrative strategies call to mind the playful techniques of Jonathan Lethem, Franz Kafka, Primo Levi and Thomas Pynchon. But she also, quite deliberately, echoes the Argentine giant Jorge Luis Borges. Like Borges, she sabotages concepts of identity, reality and place, fraying her protagonist’s ties to all three. Like Borges, she makes Argentina her favored locale for memory retrieval. And, as Borges often did, she gives her own name to a character. But there’s a still more obvious link: in his short story “Borges and I,” Borges complains of an identity crisis akin to Leo’s — albeit a crisis over his own identity, not someone else’s. There are two different Borgeses, he explains: the other Borges shares his tastes, “but in a vain sort of way that turns them into the accoutrements of an actor.” In “Atmospheric Disturbances,” Leo’s deprecating attitude toward the Rema imitator resembles Borges’s attitude toward his double. Galchen operates on Borges’s conceit, adapting it, expanding on it, giving it a new face.
If this were a different kind of novel, the central mystery wouldn’t revolve around puzzles of identity, subjectivity and objectivity. It would concern itself with the question of how an unpleasant, middle-aged, Aspergic loner like Leo Liebenstein ever managed to bag a dishy wife like Rema, with her warmth, her youth, her enticing rhythmic gait, her way of giving people “the impression that she loves them in a very personal and significant way.” In fairness, this thought had occurred to Leo. The first time the two met was at the Hungarian Pastry Shop in Manhattan. After speaking to her, ascertaining her nationality and noticing that she wasn’t edging away from him, Leo courted her by shrewdly avoiding the mention of Borges, so as not to “appear showy.” Because of this reticence, because of a mille-feuille sugar high, or for some other unknown reason, Rema succumbed to his suit. And yet, years into the marriage, Leo remains on perpetual alert, unsure of true possession, his antennae quivering to pick up any signal that Rema has discovered she’s out of his league and acted on this knowledge. He pretends he isn’t jealous. “I didn’t necessarily know at every moment exactly where she was or what, precisely, in Spanish, she said over the phone to people who might very well have been perfect strangers to me,” he admits. But that alone doesn’t mean that she “was, or is, in love with some, or many, other people.”
How reassuring. And yet, like the tormented narrator of Ford Madox Ford’s novel “The Good Soldier” — who longed to believe that his marriage was sound and that his wife was “a goodly apple,” and who began to regard other people as “incalculable simulacra amidst smoke wreaths” — after learning of her infidelity, Leo is haunted by doubts. The difference here is that Leo has betrayed himself, pre-emptively robbing himself of the possession he most values to protect himself against its loss. “Who can ever really know about anyone’s happiness, even one’s own?” he rationalizes. A true scientist, he argues, must be willing to accept “unwelcome and confounding data,” to “make discoveries that shatter one’s most deeply held beliefs.” Maybe, he adds, “we discover that a man is not an expert on himself.” Whether or not this is true, it’s certain that a hologram can’t cheat on you.
In a different kind of novel, we would sit back and watch Leo gaslight himself into wrecking his marriage, from time to time stealing glimpses through a peephole at Rema’s secret activities, if any. But Galchen and her narrator prefer radar to romance. Leo likes to picture Rema’s duplicates as figures on a Doppler weather radar pattern. “Let us imagine a source from which a Rema look-alike emerges every second,” he posits. If he “begins walking toward the source of Remas, then a Rema will pass by me more frequently than every second, even though Remas are still exiting the source at the precise rate of one per second.” He calls this the Dopplerganger effect. Immersed in one of these experiences, Leo scrutinizes the Rema mimic, noticing “fine lines of age on her face. Tiny crow’s-feet, and not just when she smiled. ... This look-alike Rema, I began to realize, was not such a perfect look-alike; it would seem Rema was being played by someone older. ... Someone pretty, but not as pretty.” Rema may not have taken a lover, but she has been manhandled by time.
You don’t have to be a weatherman to see that Galchen’s brainteasing book, whatever its pretexts, is an exploration of the mutability of romantic love. Although she has intellectualized and mystified her subject, intentionally obscuring it in a dry-ice fog of pseudoscience, the emotional peaks beneath her cloud retain their definition. The reader senses Rema’s anguish, whether or not Leo has empathy for it. Captive to his soothing psychosis, Leo can’t see his wife as anything but an impersonator, her voice “less sharp, less fiercely lovable, less accented than Rema’s,” her grip too firm, her hair incorrectly styled. He tells her, “I’ve met complete strangers who remind me more of Rema than you do,” but he’s the stranger. “It’s you,” Rema sobs, “It’s you who’s not yourself.” Anyone who has suffered the everyday calamity of the lessening of love, the infinitesimal diminutions of regard that drain a relationship of its power, knows what a relief it would be to blame science fiction. This cerebral, demanding, original new writer helps make the charges stick.