From: wecooks@ix.netcom.com
Subject: Re: Mars Global Surveyor Solar Panel Will Not Hinder Mission Goals
Date: Thu, 28 Nov 1996 07:50:34 -0800
Dear Jan, THnaks for alerting us to this news release. Since I dont' watch TV (CNN probably had the pictures already), I was imagining a one sided GS spining helplessly around Mars. Now I see it's actually just a couple of inches out of alignment. PHEW! That's easy to work around. I'll share this with my class on Monday. Hope you have/had a nice Thanksgiving! jkc On 11/27/96 14:54:56 you wrote: > >Dear discuss-lfm members, > >FYI -- news about the MGS Solar Panel! > >Jan Wee > > > >>Subject: Mars Global Surveyor Solar Panel Will Not Hinder Mission Goals > >> >>Douglas Isbell November 27, 1996 >>Headquarters, Washington, DC >>(Phone: 202/358-1753) >> >>Diane Ainsworth >>Jet Propulsion Laboratory, Pasadena, CA >>(Phone: 818/354-5011) >> >>RELEASE: 96-250 >> >>MARS GLOBAL SURVEYOR SOLAR PANEL WILL NOT HINDER MISSION GOALS >> >> Mission engineers studying a solar array on NASA's Mars >>Global Surveyor that did not fully deploy during the >>spacecraft's first day in space have concluded that the >>situation will not significantly impair Surveyor's ability to >>aerobrake into its mapping orbit, or affect its performance >>during the cruise and science portions of the mission. >> >> The solar panel under analysis is one of two 11-foot >>(3.5-meter) wings that were unfolded shortly after the Nov. 7 >>launch and are used to power Global Surveyor. Currently, the >>so-called -Y direction array is tilted 20.5 degrees away from >>its fully deployed and latched position. >> >> "After extensive investigation with our industry >>partner, Lockheed Martin Astronautics, using a variety of >>computer-simulated models and engineering tests, we believe >>the tilted array poses no extreme threat to the mission," >>said Glenn Cunningham, Mars Global Surveyor project manager >>at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA. "We >>plan to carry out some activities in the next couple of >>months using the spacecraft's electrically driven solar array >>positioning actuators to try to gently manipulate the array >>so that it drops into place. Even if we are not able to >>fully deploy the array, we can orient it during aerobraking >>so that the panel will not be a significant problem." >> >> Diagnosis of the solar array position emerged from two >>weeks of spacecraft telemetry and Global Surveyor's picture- >>perfect performance during the first trajectory maneuver, >>which was conducted on Nov. 21. The 43-second burn achieved >>a change in spacecraft velocity of about 60 miles per hour >>(27 meters per second), just as expected. The burn was >>performed to move the spacecraft on a track more directly >>aimed toward Mars, since it was launched at a slight angle to >>prevent its Delta third-stage booster from following a >>trajectory that would collide with the planet. >> >> Both the telemetry data and ground-based computer models >>indicate that a piece of metal called the "damper arm," which >>is part of the solar array deployment mechanism at the joint >>where the entire panel is attached to the spacecraft, >>probably broke during the panel's initial rotation and was >>trapped in the two inch space between the shoulder joint and >>the edge of the solar panel, Cunningham said. >> >> Engineers at JPL and Lockheed Martin Astronautics, >>Denver, CO, are working to develop a process to clear the >>obstruction by gently moving the solar panel. The damper arm >>connects the panel to a device called the "rate damper," >>which functions in much the same way as the hydraulic closer >>on a screen door acts to limit the speed at which the door >>closes. In Global Surveyor's case, the rate damper was used >>to slow the motion of the solar panel as it unfolded from its >>stowed position. >> >> Engineers have been re-evaluating the aerobraking phase >>of the Global Surveyor mission, which begins in September >>1997 after the spacecraft is captured into an elongated orbit >>around the planet using its on-board rocket engine. The >>solar arrays are essential to the aerobraking technique and >>will be used to drag the spacecraft into its final, circular >>mapping orbit. First tested on the Magellan spacecraft at >>Venus, aerobraking allows the spacecraft to carry less fuel >>to a planet and take advantage of its atmospheric drag to >>gradually lower itself into the correct orbit. >> >> "Since we launched early in our window of opportunity, >>we will not have to aerobrake as fast to reach the mapping >>orbit, and this reduces the amount of heating that the solar >>panels are exposed to," Cunningham said. "In the event that >>our efforts to latch the solar array properly in place are >>not successful, this reduced heating should allow us to tilt >>the array in such a way to prevent it from folding up and yet >>still provide enough useful aerobraking force." Additional >>analysis and testing will be performed over the next several >>months to verify this hypothesis. >> >> Meanwhile, Mars Global Surveyor continues to perform >>very well as it completes its first two weeks in space, with >>on-going science instrument calibrations being performed this >>week. At the same time, the Mars Relay radio transmitter has >>been turned on for a post-launch checkout. Radio amateurs >>around the world are gearing up to participate in a radio >>tracking experiment in which they will become receiving >>stations for the low-power beacon signal transmitted by the >>Mars Relay radio system. >> >> Mars Global Surveyor is approximately 3.4 million miles >>(5.5 million kilometers) from Earth today, traveling at a >>speed of about 74,000 miles per hour (119,000 kilometers per >>hour) with respect to the Sun. >> >> Mars Global Surveyor is the first mission in a sustained >>program of robotic exploration of Mars, managed by JPL for >>NASA's Office of Space Science, Washington, DC. >> >> -end- >> >>Note to Editors: A line-drawing of Mars Global Surveyor >>showing the current position of the solar panel in its fully >>deployed position, including a blow-up which shows the area >>in which the broken deployment mechanism is located, can be >>found under "News Flashes" on JPL's World Wide Web home page >>using the following URL: http://www.jpl.nasa.gov >> >> > > >