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NASA Managers Decide to Give Nine Hours of Additional Mapping to Shuttle Mission The original plan for the STS-99 SRTM mission called for 10 days of mapping the world, enough to cover 100% of the land areas between 60 degrees North and 55 degrees South. But just ten days before the planned launch managers decided to take the precaution of retracting the mast a day early, sacrificing approximately 10% of the mapping orbits. The spare day could be used for an emergency spacewalk if necessary to retract the boom manually. But scientists refused to give up on trying to get back the additional day. Project Scientist Mike Kobrick said "The door isn't closed because I've stuck my foot in it." On Friday evening managers agreed to restore nine hours of mapping. When shuttle commander Kevin Kregel was informed he replied "That's super news, we sure want to give the customer as much data as we can." The tradeoff is no opportunity to retract the mast manually on a spacewalk. So if the mast jams during retraction, now scheduled for Monday February 21 at 6:43 am, the shuttle crew would have to flip the switches to jettison the mast and outboard antenna overboard. The odds for a problem during the retraction are small and the nine extra hours will provide the opportunity to map more of the world. Every 90 seconds SRTM maps the equivalent area to the state of Florida. In the additional 9 hours the shuttle will make six more orbits of the world and roughly an additional 3% of the world map. Kobrick said "It's worth a lot." The failure of the cold gas thruster resulted in additional use of shuttle propellant. Engineers were able to conserve propellant on the shuttle through innovative techniques including combining three reboost maneuvers in to two, relaxing the limits on how tightly the shuttle held its orientation, and how waster water was dumped overboard. Consequently there isn't enough propellant to extend the mission back to the original preflight plan of 10 days of mapping. Nevertheless the additional nine hours will result in the mission accomplishing about 95% of its original objective of 100% of the land areas of the world between 60 degrees North and 55 degrees South. SRTM scientists have been releasing 'quick-look' images (see Image Gallery) based on the small percentage of the data which has been radioed to the ground. A recent three dimensional perspective relief - see Image Here - shows how different forms of GIS data from different sources can be combined to create a more useful database than the individual images. SRTM elevation data was combined with the natural colors from a Landsat image and a high resolution digitized aerial photograph to generate an impressive view of Pasadena California, the home of NASA's Jet Propulsion Laboratory and the SRTM payload. Vertical lines in the image aren't artifacts, they're roads in the urban region. Other visible features include the Rose Bowl and its adjacent golf course and Interstate highways. 
The graphic above shows where the shuttle will fly in the additional 9
hours of mapping. Some of it was previously mapped on single passes. The
9 additional hours will permit those areas to be fully mapped from two
perspectives. Please contact the Editor for additional details.
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Exclusive - Shuttle Mission Begins Its Ambitious Map of the World (Feb. 12, 2000)Copyright© 1995-2012 MindSites Group / Privacy Policy
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