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Answers Your Questions

From: Jenny Spravsow, of Sterling Heights MI
To: Bill Reeves, flight director for the planning team

Question: In the split screen animated views of the Discovery, it appears that the shuttle is moving backwards with respect to earth. Is it really traveling backwards "nose last" or is the earth merely going faster, creating the optical illusion? Thanks Jenny PS, I watch NASA TV as often as possible when there is a mission. Its excellent education!

Answer: The shuttle was indeed "flying backwards". This attitude is called -ZLV -XVV. The payload bay (the negative Z axis of the shuttle) points at the Earth and defines the Local Vertical Axis (-ZLV)and the tail of the shuttle (the negative X axis) points into the Velocity Vector or direction of travel (-XVV). After undock from the International Space Station, you might notice the shuttle flying in a -ZLV +YVV attitude, where the wing of the shuttle will be pointed in the direction of travel. This attitude is used when water is being dumped overboard. The attitude that we fly is driven by thermal conditions, minimizing propellant consumption, maximum power generation from the solar arrays, and providing pointing of our antennas for communications.

Michael Moses
Orbit 2 Propulsion Officer

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Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 04/07/2002
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