NASA's Mars Odyssey Enters Orbit

maddmike writes "Nasa's Mars explorer Odyssey is scheduled to brake and orbit about Mars today at 7:30PDT. Among the mission's objectives are to understand Mars' climate and geological history and to search for signs of life sustaining environments including water. Main web site is at the JPL website." Update: 10/24 13:12 GMT by T : The BrownFury writes cites a Space.com summary which says "The Mars Odyssey spacecraft appears to have succeeded Tuesday night in one of the most tricky and critical parts of its missions by slipping into orbit around the Red Planet."

Comments

Teflon was *not* a spinoff.

[kaszeta]

After all, space research has lots of practical spin-offs, like teflon for example.

Why does everyone feel the need to falsely attribute various inventions as space program spinoffs?

Teflon was invented in 1938, well before anything that could even remotely be considered modern space research.

Don't get me wrong, space research is good, and it produces a valuable product: knowledge.

False attributions to the space program don't help with their budget problems, though. I'm not blaming you, however, NASA themselves is quite guilty of exaggeration.

Distance, reliability

[s20451]

1. When the spacecraft first goes into orbit, you want a reliable, simple telemetry signal to indicate the basics of what is happening with the spacecraft. This means a low-gain, wide-beam transmitting antenna. The high-gain antenna will provide higher rates, but must be aimed much more carefully; such a system would not be robust if something went slightly wrong during orbit insertion.
2. From the Where is Mars Odyssey Right Now? page, the spacecraft is currently 1.53e+11 meters from Earth. Even with a directional antenna, signal power drops with distance squared, so the path loss is on the order of 200 dB. That is, if the transmitter power is (say) 50 watts/m^2 at 1 meter away from the spacecraft, as measured from Earth it would be something like 10^-20 watts/m^2, not counting antenna gains. At those powers you'd be lucky to get 40 bits/s, simply by running into Shannon's limit. (Somebody check my math, I haven't had coffee this morning.) Imagine the communications challenge for Voyager 2, which is now heading out of the solar system at a range of billions of kilometers; or Galileo, which lost its high-gain antenna at Jupiter ...