Accurate rendering

It is very rare when a journalist takes time to understand issues and put them in a language that is not technical yet still understandable to the public. Phil Chien seems to have done so in his article published in the Eagle on the experiments that took place during Columbia's final journey.

During space shuttle Columbia’s final, 17-day mission, a large amount of scientific data was relayed to the ground. When the shuttle broke up over East Texas on Feb. 1, 2003, it was feared that all of the science aboard had been lost, in particular biological samples....

Texas A&M University had two experiments onboard — a rat experiment sponsored by the College of Veterinary Medicine and “StarNav,” a prototype star tracker built by students at the Spacecraft Technology Center.

The StarNav team’s goal was to design an inexpensive star tracker to determine the shuttle’s attitude, or orientation. A digital camera was mounted in a tube with a single-board computer. The computer converted those images into readable star charts, and its Lost In Space Algorithm (LISA) program calculated the spacecraft’s orientation. The software has to isolate debris and other unwanted defects in the photos so accurate star patterns can be determined.

There was a problem — the StarNav team had not anticipated too much stray light entering the camera. Before the mission, the team made a list of restrictions for when the instrument could be turned on: no viewing the sun, moon, or brightly lit Earth, or when Columbia was passing through a high radiation region over the South Atlantic Ocean.

You can see this in the following photo (we are behind the white box on the center right on top of the Spacehab module.)

Even the camera that took this shot sees a lot of reflections. We were not expecting that much glare, so we had to change the whole shooting schedule to make photo shoots only when the orbiter was on the night side. This led us into scheduling new star pictures sessions that were originally not on the agenda (after the normal clearance process with SpaceHab and NASA) since most of our shooting sessions seemed to occur when the orbiter was on the day side during most of the mission. We did get a lot of night shots but as Phil says,

Unfortunately, six days after launch, StarNav was powered while going through the high-radiation region. Its hardware was built from non-radiation-hardened components and, not surprisingly, it stopped working.

This high radiation area was the SAA. But it was still a surprise to us.

The StarNav team could not send commands to shut off the unit in time because of other higher-priority communications. Later, a maintenance procedure was sent to the crew to instruct them to use a laptop computer to send commands to the payload.

“Eventually we had to stop, as the camera never was able to perform the duties that were expected from it [after the radiation problems],” scientist Igor Carron said.

Even with those problems, StarNav was a success. The main purpose was for the students to develop a technique that could be used on future spacecraft sensors. They were able to design their star tracker and build it from off-the-shelf electronics, test it ahead of time to ensure it would work in outer space, and make it safe enough to fly on the shuttle.

All together, they had 30 25-minute opportunities to use StarNav, and they received 32 digital images. The onboard computer was able to use those images to determine where the instrument was pointed.

The goal for the experiment was a prototype star tracker, and that was extremely successful. The problems the StarNav team encountered were good problems because they showed the limitations of their concept and where they needed improvements. Texas A&M has used the knowledge from StarNav to develop the Khalstar Star Tracker, which is commercially available.

... For most of the scientists the loss of their life’s work seemed insignificant in comparison with the loss of the seven person crew and the space shuttle.

Scientists who were able to recover their experiments from the debris or had data radioed during the mission are doing whatever science they can.

In a strange twist, the web site on which we described our experiment was, unbeknownst to us, used by members of the recovery team in Florida to figure out that two pieces of equipment found 100 miles north of College Station were coming from our camera.

Philip Chien will publish a book about the Columbia astronauts and their mission entitled "Columbia — The Final Voyage of NASA’s First Space Shuttle."