IGY Bulletin, Number 9, March 1958 - Phototrack

Back to the IGY Bulletin articles. Phototrack was the designation for the program utilizing volunteers to help track Earth satellites, as noted in a previous post.

Accuracy of these observations was deemed to be "quite high," limited by timing accuracy, which was 0.1 seconds.

Photographs were taken against a fixed starfield background which yielded satellite positions. Timed breaks were inserted in the image used to track the satellites. 

Image showing the tracking of Earth Satellite 1957β, i.e. Sputnik 2 (from the Bulletin article)

Times were determined with a Phototrack camera by photographing a clock three times per picture, leaving a time mark on the image of the starfield and satellite. The clock was synchronized to radio station WWV, run by the National Bureau of Standards (now the National Institute of Standards and Technology).

Photographing the clock for timing marks (from the Bulletin article)

Other specifications for the Phototrack system are given in the Bulletin article. 

There is a Wikipedia article that summarizes this Phototrack program. There is also a nice personal recollection of participation in the Phototrack program by John Sutherland. He started worked at the Phototrack 5007 tracking operation in Walpole, MA, that had been set up during the IGY by Warren Davis and others. I tried to email Sutherland, but that was bounced back. Sutherland reminds us that "all of this ‘space’ activity happened in the slide rule era – there were no computers to help with the calculations, in fact, there were not even any hand calculators. Everything was done manually and by knowing how to create and use formulas." One of the Wikipedia article citations is "Seven Place Cosines, Sines, and Tangents For Every Tenth Microturn." That sounds pretty brute force.

My antique slide room, vintage 1972

In my undergrad days of the late 1960s and early 1970s, all calculations were done with slide rules; tables of various mathematical functions were also very useful. At some point I lost my trusty K&E slide rule, which I used daily for four years. I still own the replacement shown at right, now gathering dust on my electronics museum shelf.

The history of the slide rule goes back to the early 17th century. There is not a single postage stamp honoring the slide rule, but I think there should be!

In my first real job at Fairchild after graduation, I used a desktop mechanical calculator, a wonderful machine. My father had used one at home to work on his accounts. In grad school I finally used digital calculators, followed by programmable calculators, and then mainframe computers with terminals in the lab where I worked. It wasn't until the very end of grad school that I saw my first Apple personal computer, and then used and bought an original IBM PC soon after I started my job at Franklin & Marshall College in 1983.

My first IBM PC from 1983-84 (right); a later iMac (left)

These older technologies make me think of the women calculators of NASA, and the book and movie Hidden Figures. Kudos to trailblazer Katherine Johnson and her colleagues!