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STARSHINE UPDATE June 25, 1999
Here are some NASA photos of Starshine being remotely deployed from Discovery’s cargo bay by Canadian astronaut Julie Payette at 2:21 A.M. CDT (0721 GMT) on June 5, 1999.
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When Julie responded to a question from Shuttle Mission Control in Houston about how the deploy had gone, she sang out, in her beautiful French accent, “Good Morning, Starshine…. It’s out there.” When U.S. astronaut Dan Barry was later describing the sight as the satellite floated out of its canister into sun light, he exclaimed, “It was just an explosion of light!”We do need to let you know that Starshine’s mirror flashes are much less frequent than we expected them to be. The reason is that the NASA Hitchhiker ejection system did such a precise job of deploying our spacecraft that it didn’t tumble or spin like we expected it to. The Mightysat spacecraft that was deployed by this same Hitchhiker ejection system on the STS-88 mission in December of 1998 tumbled and spun at a combined rate of about one revolution per minute. That’s what we expected to happen when Starshine was deployed; however, the Hitchhiker program office made some improvements to the ejection system between the two missions. We now think that may be the explanation for the fact that Starshine neither spun nor tumbled at all while it was in the field of view of the Shuttle cameras.
Observers on the ground will therefore not see the planned mirror flash rate of approximately once per three to five seconds, early in the mission. In fact, reports received thus far from several dozen observers in different parts of the world have indicated they have seen flash rates ranging all the way from once per five seconds, to once per twenty seconds, to once or twice per pass, to nothing at all. This is due to the fact that the only effect that is producing flashes at this time is the orbital motion of the satellite across the sky. The relative geometry of the sun, the satellite and the observer, combined with the way the rows of mirrors are aligned on the satellite, determines how many flashes a given observer will see on a given pass. Therefore, this early in the mission, Starshine will just go floating along in inertial space, neither tumbling nor spinning, and it is going to be rather difficult to track precisely, since you won’t be sure whether it will flash at just the right time for you to mark the time it passes between a pair of target stars.
We do expect the flash rate to increase, later in the mission, as Starshine descends into denser air and begins to experience aerodynamic forces. The satellite should eventually start to act like a wobbling badminton shuttlecock, due to the fact that the deployment foot at its base will act like the shuttlecock’s feathers and cause it to face round-end forward and wiggle back and forth, as its zips along at five miles a second through the air. At that time, we can go back to the standard method of tracking the satellite and reporting your data. In the meantime, however, we’re not sure at just what altitude that effect will produce a meaningful increase in flash rate, so we need your help to find out. You can find out when Starshine flashes might be visible at your location by clicking HERE. Please obtain a digital wrist watch equipped with a seconds display, synchronize it with the National Institute of Standards and Technology (NIST) time clock displayed HERE, and write down the times that you see Starshine’s mirror flashes. Set up a users account, click HERE, log in to your account and report your flashes to us HERE.
The good news is that Starshine’s orbit is gradually decaying, just as expected. The satellite’s average orbital altitude above the surface has decreased by approximately two kilometers since it was deployed on June 5. You can see a plot of this effect, courtesy of Chris Peat, by clicking HERE. You can also see a daily image of the Sun, courtesy of the Big Bear Observatory, by clicking HERE and counting sunspots. To figure a daily sunspot number, count the big clusters of spots, multiply that number by ten, and add it to the number of the individual spots you can see.
So, in summary, let’s shift our emphasis, for now, to measuring when Starshine’s flashes occur and comparing the increase in their rate of occurrence with the daily decrease in the satellite’s orbital altitude. Let’s also see if we can observe a relationship between sunspot population and rate of decrease of satellite altitude. We’ll make a decision later on about when it’s time to shift back to the regular observing and reporting process. By the way, the nominal mission lifetime is now expected to be eight months, so get ready to ring in the new millenium by watching for Starshine to end its life in January of the year 2000 as a blazing fireball somewhere in the world.
Gil Moore
Director
Project Starshine
