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Thursday, August 05, 2004

Brazil's Amazonas Satellite Reaches Space

A Russian rocket successfully launched the largest telecommunications satellite ever to serve Spanish-speaking customers in Latin America - as well as North American and European markets - into space during a Tuesday evening flight.
Sitting atop a Proton-M launch vehicle, the Amazonas satellite rocketed away from its staging grounds at Baikonur Cosmodrome in Kazakhstan.
"The Amazonas satellite will revolutionize communications in Brazil and across the Americas," said Mark Albrecht, president of the McLean, Virginia-based International Launch Services (ILS), which marketed the launch.
The Amazonas satellite lifted off from Baikonur's Launch Pad 39 at 6:32 p.m. EDT (2232 GMT), the first step in its journey into orbit. A Breeze M upper stage was expected to deliver the spacecraft into a geosynchronous transfer orbit about nine hours and 11 minutes into the flight. Spacecraft separation was expected to occur at 3:45 a.m. EDT (0745 GMT) on Aug. 5.
Amazonas was built by France's EADS Astrium for the telecommunications firm Hispamar, a Brazilian subsidiary of Hispasat in Spain. The spacecraft weighs about 10,020 pounds (4,545 kilograms) and is based on EAD's Eurostar E3000 satellite platform. Its mass, combined with satellite's 63 transponders, makes Amazonas the largest ever launched for Latin American telecommunications services. It is also the most powerful satellite in the Hispasat fleet.
"Amazonas is the most important satellite for Latin America," said Hispasat chairman Luiz Perrone. During its 15-year designed lifetime, the satellite will be managed from a control center in Rio de Janeiro, he added.
Amazonas carries 36 Ku-band transponders and 27 C-band transponders designed to expand Spanish-speaking telecommunications from the basic television broadcasting to include Internet, corporate communications and broadband applications. In addition to providing telecommunications services to both North and South America, Amazonas will also serve parts of Europe as well.
The successful Amazonas launch marked the third Proton launch for ILS in 2004 and the seventh successful flight overall this year. The group's next launch, a classified payload for the National Reconnaissance Office to ride an Atlas 3AS, is slated for Aug. 27 using an Atlas 2AS rocket.

Weak Version of Most Powerful Explosions Found

Gamma-ray bursts are the most powerful events in the universe, temporary outshining several galaxies and likely signaling the birth of a black hole.
But astronomers have been puzzled by one burst, noted in 1998, that was comparatively dim. Was the weakling a loner, a total "freak" as one astronomer termed it? Or have others like it simply gone undetected.
The answer is written in this week's journal Nature, in which scientists tell of another weak gamma-ray burst. With two in the books and more expected, astronomers are now confident there is a whole range of strengths of these interesting flashes of high-energy radiation.
Mysterious bursts
Gamma rays are part of the electromagnetic spectrum of radiation, which includes long and lowly radio waves on one end, visible light near the middle, and X-rays toward the high end. Gamma rays are the most energetic, having the shortest wavelength.
Gamma-ray bursts, also called GRBs, were first noticed in the 1960s. In just a few seconds or less, an extreme outburst can put out as much radiation as several galaxies. The bursts typically occur outside our galaxy, many billions of light-years distant. Their brevity makes them hard to study.
In recent years, however, observations have linked gamma-ray bursts to the formation of black holes immediately after supernova events, the explosive ends to massive stars' lives. The gamma rays shoot out in two opposing jets along the rotation axis of the black hole. Only those bursts that are beamed directly at us can be seen with present technology, because gamma rays don't stray far from their beamed direction.
Meanwhile, most supernovas don't emit detectable gamma rays. Instead, just an expanding ring of other radiation is noted.
Closer at hand
A gamma-ray burst on Dec. 3, 2003 was detected by the European-Russian Integral satellite. Other telescopes on the ground and in space examined the event's afterglow in radio, visible light and X-rays. The eruption, catalogued as GRB 031203, was relatively nearby at some 1.6 billion light-years away.
Being close, it ought to have been bright. But GRB 031203 was about one-thousandth as strong as other gamma-ray bursts. Scientists are calling it a sub-energetic gamma-ray burst that resembles the 1998 event.
The finding fits theoretical expectations, showing the 1998 burst "was not a freak event, and in fact there are probably many more sub-energetic GRBs like this out there," Caltech graduate student Alicia Soderberg, lead author of one paper in the journal, told SPACE.com. "The fact that they are sub-energetic makes them fainter and therefore harder to detect."
That suggests there is a relationship between the strongest and weakest stellar explosions, and that there is a continuum of events in between with differing outputs, Soderberg and her colleagues say.
More to find
Sub-energetic gamma-ray bursts will one day outnumber their more powerful cousins once more sensitive telescopes are put on the case, the researchers believe.
"This is an intriguing discovery," said Caltech Professor Shrinivas Kulkarni. "I expect a treasure trove of such events to be identified by NASA's Swift mission scheduled to be launched this fall from Cape Canaveral. I am convinced that further discoveries and studies of this new class of hybrid events will forward our understanding of the death of massive stars."
Two papers on the burst are published in the Aug. 5 issue of Nature. The lead author on the other is Sergey Sazonov of the Space Research Institute of the Russian Academy of Sciences.
"The idea that all GRBs spit out the same amount of gamma rays, or that they are 'standard candles' as we call them, is simply ruled out by the new data," Sazonov said.

Glitches Dog Both Mars Rovers

In a prelude of more problems that are likely to arise, both of NASA's Mars rovers experienced glitches this week as they plow through unknown engineering territory, operating well beyond what the mission blueprints called for.

The twins are working at reduced capacity while project managers try to figure out what's wrong. Both rovers had 90-day primary missions and have more than doubled that time on the surface of the red planet.

Spirit is climbing the rocky Columbia Hills of Mars, examining bedrock for signs of past water.

While executing commands on Aug. 1, a semiconductor component on Spirit failed to power on as intended, according to a NASA statement issued today. The component, a programmable gate array, directly affects usability of the rover's three spectrometer instruments, which analyze light from various targets.

Fix likely

Subsequent commands for using the miniature thermal emission spectrometer in that day's sequence resulted in repeated error messages.

The most likely cause is a timing issue of one instruction reaching the gate array microseconds before another that was intended to precede it, engineers have determined. If that diagnosis is confirmed, a repeat could possibly be avoided by inserting a delay between commands that might reproduce the problem. Until then, Spirit cannot use the miniature thermal emission spectrometer, the Moessbauer spectrometer or the alpha particle X-ray spectrometer.

"While we're being very cautious in how we operate today and tomorrow, we expect to verify the problem and resolve this issue with a relatively easy workaround," said Jim Erickson, project manager for the twin rovers at NASA's Jet Propulsion Laboratory.

Already, Spirit has been driving backwards on just five of its six wheels, since the right front wheel developed extra resistance in July. Managers are saving the wheel for use only when it is truly needed.

Spirit has traveled more than 2.1 miles (3.5 kilometers) since landing in January.


On the other side of the planet, Opportunity has driven about 66 feet (20 meters) into Endurance Crater, looking at older bedrock with each step down. The rover's odometer is nearing 1 mile (1.5 kilometers) for its entire mission.

Four times in the past two weeks, Opportunity has sent error messages while successfully taking pictures with its microscopic imager, officials said. The problem might be related to degradation of flexible cabling that runs down the rover's robotic arm to the instrument.

As a precaution, the rover team is being cautious about using the arm while they try to diagnose the problem.

"We are being very conservative about this because we certainly don't want to do anything to jeopardize the instruments," said Ken Herkenhoff of the U.S. Geological Survey Astrogeology Team, Flagstaff, Ariz. And lead scientist for both rovers' microscopic imagers. "We are running more diagnostics that we hope will identify the problem."

There are potential explanations might lead to restoring full use of the arm. But mission managers know the rovers' days are ultimately numbered.

"We will no doubt have more issues with them in the future," Erickson said. "We'll do everything we can to milk the most value out of them while they are usable, but they won't last forever."

Saturn's South Pole

A dark spot marks Saturn's south pole in this new image from the Cassini spacecraft. It was taken July 13 and released yesterday.

Around the polar region, concentric rings of clouds can be seen. To the north, wavy patterns are evident, resulting from the atmosphere moving with different speeds at different latitudes. Other observations have revealed that Saturn's winds change dramatically over time, having slowed down by 40 percent over two decades.

Cassini was 3.1 million miles (5 million kilometers) from Saturn when it snapped this infrared view. Contrast has been enhanced slightly to aid visibility.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. It is run out of the Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena. The imaging team is based at the Space Science Institute, Boulder, Colorado.

Aura Post-Launch Status Report

Alan Buis 818/653-8339 Jet Propulsion Laboratory, Pasadena, Calif.
Lynn Chandler 301/286-2806Goddard Space Flight Center, Greenbelt, Md.
Gretchen Cook-Anderson 202/358-0836Headquarters, Washington
NEWS RELEASE: 2004-192 August 4, 2004

Activation of the Aura spacecraft, launched July 15, is continuing, with the mission going very well so far.
Just over an hour after launch, the spacecraft separated from the Boeing Delta II launch vehicle. This was followed shortly thereafter by deployment of the spacecraft's solar array and transition to Sun point mode. The next day, the spacecraft transitioned to Earth point mode, where it remained another day before transitioning to fine point mode, the mission's normal operating mode. S-band communications with the space network began immediately, followed by routine ground network contacts. X-band playbacks from the solid-state recorder to the ground network are now ongoing as well.
All spacecraft subsystems have demonstrated readiness to support science operations, which cannot begin until the instruments are fully activated and Aura has reached its nominal orbit altitude.
With respect to orbit altitude, four of six planned ascent burns have been completed. The fifth ascent burn is planned for Fri., August 6. The Aura ascent plan anticipates reaching a nominal altitude of 705 kilometers (about 438 miles) this month.
All four instruments are powered and are systematically being activated; the following are some of the highlights that have occurred so far. The antenna launch latch for the Microwave Limb Sounder primary reflector has been released, and the receivers are undergoing characterization activities. Good output power from the Microwave Limb Sounder THz module gas laser local oscillator has been confirmed. The Tropospheric Emission Spectrometer translator has been unlatched, as has that instrument's pointing control system gimbals. The Sun-shield door for the High Resolution Dynamics Limb Sounder has been released. Transition of the Tropospheric Emission Spectrometer, High Resolution Dynamics Limb Sounder and the Ozone Monitoring Instrument to science mode is paced by their significant outgassing requirements, which last about 30 days.
"From what we have seen so far, satellite performance appears very solid," said Rick Pickering, Aura project manager at NASA's Goddard Space Flight Center, Greenbelt, Md. "Also, the performance of the entire operations team has been tremendous. Not only are all the team members inherently sharp and well-trained, many of them have extensive experience with Aqua, which is paying great dividends."
Aura, a mission dedicated to the health of Earth's atmosphere, will help us understand and protect the air we breathe. Aura will help answer three key scientific questions: Is Earth's protective ozone layer recovering? What are the processes controlling air quality? How is Earth's climate changing? NASA expects early scientific data from Aura within 30 to 90 days.
Each of Aura's four instruments is designed to survey different aspects of Earth's atmosphere. Aura will survey the atmosphere from the troposphere, where mankind lives, through the stratosphere, where the ozone layer resides and protects life on Earth.
With the launch of Aura, the first series of NASA's Earth Observing System satellites is complete. The other satellites are Terra, which monitors land, and Aqua, which observes Earth's water cycle.
The High Resolution Dynamics Limb Sounder was built by the United Kingdom and the United States. NASA's Jet Propulsion Laboratory, Pasadena, Calif., developed and manages the Microwave Limb Sounder and Tropospheric Emission Spectrometer. The Ozone Monitoring Instrument was built by the Netherlands and Finland in collaboration with NASA. NASA's Goddard Space Flight Center manages the Aura mission.
The Microwave Limb Sounder is intended to improve our understanding of ozone in Earth's stratosphere, which is vital in protecting us from solar ultraviolet radiation. The Tropospheric Emission Spectrometer is an infrared sensor designed to study Earth's troposphere and to look at ozone and other urban pollutants.
For Aura information and images on the Internet, visit:http://jpl.convio.net/site/R?i=0C7rkJ4nMtlO-3BCLCXxIg.. ; and http://jpl.convio.net/site/R?i=hGj0WOu_vvRO-3BCLCXxIg.. .
For more information about the Microwave Limb Sounder, visit:http://jpl.convio.net/site/R?i=0WtYime84DlO-3BCLCXxIg.. .
For more information about the Tropospheric Emission Spectrometer, visit:http://jpl.convio.net/site/R?i=upYlZAJ0GllO-3BCLCXxIg.. .
The California Institute of Technology in Pasadena manages JPL for NASA.