Satellite bumped out of formation to avoid potential collisions

French PARASOL satellite maneuver avoids adding to space debris problem

CNES PARASOL satellite
French space scientists said they had moved one of the key Earth-observing satellites out of its orbit with four NASA satellites to avoid potential collisions. 

The French satellite, known as PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar) was flying in a constellation of satellites known as the A Train. The A-Train satellite formation consists of NASA's  Aqua, CloudSat, CALIPSO, and Aura.  

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According to NASA, the A Train formation allows more information about climate changes on Earth to be gathered simultaneously than would be possible from the sum of the observations taken independently.  NASA notes the A Train formation is also known as the Afternoon constellation and crosses the equator in the early afternoon and also in the middle of the night, at about 1:30 a.m. and is separate from another satellite formation, known as the morning constellation made up of Landsat-7, EO-1, SAC-C, and Terra. 

The A-Train satellites also provide unique information about tropical cyclones, the collective term for tropical depressions, tropical storms, hurricanes and typhoons, NASA said.

The French Space Agency (CNES) said that after collecting observations synchronous with the other satellites from the A-Train for almost 5 years, PARASOL was moved to a lower orbit 2.4 miles (3.9 km) under the A Train after CNES noted PARASOL orbit tracks slowly drifting eastward over the past these past few months.  

CNES's said its decision to position PARASOL to a lower orbit was motivated by safety reasons to minimize the risk of collision, should PARASOL begin to fail (PARASOL, flew within about 10 minutes of the others).  While the expected duration of the PARASOL mission was 2 years, it will reach 5 years in March 2010. 

In the new orbit, observations from PARASOL will no longer be simultaneous with the others, except for only a few days at regular intervals, NASA said. 

Avoiding space debris is a hot topic these days.  In fact the A Train has already had experience with it.  NASA has noted that the Aqua satellite in November successfully performed its first ever Debris Avoidance Maneuver to avoid a piece of the Chinese Anti-Satellite (ASAT) missile test debris from January 2007. 

We are coming up on the year anniversary of the accidental collision of American and Russian spacecraft and the cataloged debris population has grown by nearly 40%, in comparison with all the debris remaining from the first 50 years of the Space Age, experts say. 

NASA's Nicholas Johnson, Chief Scientist for Orbital Debris at the Johnson Space Center told a congressional hearing last year that  the United States Space Surveillance Network, managed by U.S. Strategic Command, is tracking more than 19,000 objects in orbit about the Earth, of which approximately 95 % represent some form of debris. However, these are only the larger pieces of space debris, typically four inches or more in diameter. The number of debris as small as half an inch exceeds 300,000. Due to the tremendous energies possessed by space debris, the collision between a piece of debris only a half-inch in diameter and an operational spacecraft, piloted by humans or robotic, has the potential for catastrophic consequences, he stated.

However, these are only the larger pieces of space debris, typically four inches or more in diameter. The number of debris as small as half an inch exceeds 300,000. Due to the tremendous energies possessed by space debris, the collision between a piece of debris only a half-inch in diameter and an operational spacecraft, piloted by humans or robotic, has the potential for catastrophic consequences.

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