Amateur Astronomers Association of Princeton

by Arshad Jilani

Canopus is a bluish-white star, about 300 light years away. This star, the second brightest in the sky after Sirius, became a major focus of my life, thirty-five years ago.

In April, 1977, I moved from the Philadelphia area to Pasadena, CA, to work on assignment with NASA at the Jet Propulsion Laboratory (JPL), from my parent company, General Electric. This was early in my career, where I had been working in GE’s Aerospace Business on missile reentry systems, robotic manipulators, control algorithms for Space Shuttle manipulator prototypes and other such esoterical projects. In the summer of 1976, NASA’s Project Viking, the first successful attempt at soft landings on Mars, had put two Landers on the planet, each with an associated Orbiter. One section of the Viking Flight Team was called the Orbiter Power Analysis Group (OPAG), which was staffed by GE.

I, along with two colleagues from Philadelphia, was asked if I would like to work on the Viking program. All of us, being single and early in our careers, jumped at this unusual opportunity. Upon arrival at JPL, we were each given different assignments in OPAG; mine was to work on the Canopus Trackers of the two Orbiters. As JPL employees, we were also Caltech faculty. We also had to very quickly familiarize ourselves with a million acronyms, as NASA-speak is totally unintelligible without knowing these.

The Canopus Star Tracker (CST) is a small ‘telescope’ mounted on spacecraft to provide orientation to the vehicle by acquiring reference stars during and after planned maneuvers. These trackers are upgraded with the latest optical and electronic technology each time a new spacecraft is launched into space. During maneuvers, a vehicle drifts ever so slightly from its planned trajectory, and without being able to track a specific reference star, it would be very difficult to return the spacecraft to its intended path. The CST is a very sensitive instrument and, like other devices on a spacecraft, degrades over time due to particles settling on the lens and deterioration of its light detectors. The star Canopus, which gives its name to the device, is used to periodically re-calibrate the Tracker and gives us a measure of deterioration of the optics over time.

My task was twofold. First, I had to select the stars to be used for roll reference and secondly, I had to determine the deterioration of the device so that tracking calculations could be upgraded to reflect the lat-est baseline.

I had been a casual rooftop astronomer from the age of fifteen, when a friend, whom I met on a visit to Sri Lanka, showed me the fascinating sight of Jupiter and its moons through his six-inch refractor. At eighteen, in my hometown of Peshawar, Pakistan, my mother got me a three-and-a-half-inch Newtonian which I used every evening on the flat roof of our house, which was located in a sparsely populated area, on the edge of town. In those days (the late sixties) you could clearly see the sky at night including the Milky Way and such dim features as the Andromeda Galaxy with the naked eye. This, as in most metropolitan areas of the world, is no longer true.

My knowledge of the stars made my task at JPL much easier than it might have been. I had to look at many factors to determine which star to recommend as a reference before a maneuver could take place. One of the major challenges was that during a maneuver, we had to avoid any star that might enter Mars Straylight. Mars Straylight refers to unwanted light that could enter the CST from the surface of Mars or due to the proximity of sunlight during maneuvers. A lot of time was spent finding ‘bright’ stars that would remain in the ‘dark’ throughout and immediately after the maneuver. After pouring over printouts of star intensities and Mars Straylight maps I would select the reference star to be used. Each week, I would provide my selection by Tuesday, which, along with maneuver commands, would be uplinked to the Orbiter on Wednesday. Typical maneuvers included thematic mapping of the Mars surface, picture taking, etc. Maneuver results would be received at JPL by Thursday. These results would be reviewed on Friday along with requests for the next week’s maneuvers, and the cycle would be repeated all over again. The data received from maneuvers was reviewed, each week, by several astronomers such as Carl Sagan and others, to determine the next steps.

One time we were having a hard time finding a satisfactory star because Jupiter kept popping into the Tracker’s field of view. I suggested using Jupiter instead of fighting it, due to the short length of the maneuver, and to my surprise, my suggestion was accepted and it was added to the list of reference ‘stars’ for space missions.

With my knowledge of robotics, I also worked, informally, with the Viking Lander team on tricky problems that would arise from time to time with the robotic arms on the Landers. I also got to know some of the leading experts in robotics, who were at JPL at the time, and was able to participate in discussions of future planetary rovers.

While working on Viking, we received a letter of congratulations from President Jimmy Carter and the prestigious NASA Goddard Award.

I made many friends among the Viking Mars community and joined the JPL Ski Club. In addition, I was able to visit Mt. Wilson Observatory a number of times to satisfy any observational desires.

This experience, working across so many disparate teams, had a major impact on my successful thirty-seven year career in GE, spanning many countries in Europe and Asia, and was extremely rewarding for my family also, who moved with me on several of my assignments.