Pioneer Venus, 1978
Martin Tomasko I proposed for a Venus entry probe mission, Pioneer Venus, and we got selected and we built a photometer to measure the penetration of sunlight through the atmosphere of Venus as the probe comes down in a parachute through the atmosphere of Venus. How thick are the clouds? How much sunlight gets absorbed in the clouds? How much gets absorbed down to the ground and can drive the greenhouse effect that would be responsible for the high temperature on the surface of Venus?
We found something like two and a half percent of the sunlight makes it through the clouds and gets absorbed at the ground, and that’s enough, we think, with a thick thermal blanket in Venus’ atmosphere, to explain the greenhouse effect.
But it was interesting, too, proposing for that mission, getting selected, working with an aerospace contractor to built the electronics. The optics was designed here, actually in Optical Sciences Center. The sensor head was built in the Optical Sciences Center; it was calibrated here in Tucson, and then delivered and flown. We finally got to answer the questions ten years later that we proposed in the original proposal of how much sunlight gets absorbed in Venus’s atmosphere. That was really exciting, too.
Marty Tomasko was my thesis advisor. We got a contract to do Pioneer Venus, which came along in ’78. It was an entry probe. We had an instrument on Pioneer Venus called the solar flux radiometer, and it parachuted down into Venus’s atmosphere and it got down to about, I don’t know, 20 kilometers or so, when apparently the solder melted, and it quit working; it got too hot. But we built that here largely, we did all the testing of it here, and I had a lot of experience in building and flying instruments by that time.
I had worked with Marty Tomasko when I was a student. After graduation, he hired me to help calibrate an instrument that he was sending to Venus. I worked for two or three months helping him calibrate this instrument. It was delivered to the spacecraft team in June, the launch was in August and it landed on Venus in December. A month later we had a paper in Science magazine. A few months after that I was writing programs for the thermal balance of the Venusian atmosphere, and thought of myself as a Venusian weatherman. This is great, what a wonderful career, exploring planets.