Rocket-borne experiments

What was the topic for your initial work with the rockets, and how did you select it? And is it true that the laboratory experiments were pretty well in tandem with the airborne or high-altitude ones?

I looked for simple things to do, and they were pretty simple. We took the absorption of ultraviolet radiation in the atmosphere as the problem, because that was close to the sorts of things I understood, and I rationalised it a lot. The typical absorption thing was the Lyman-alpha radiation function. That radiation was very important because it is the fundamental line of the simplest atom and the dominant radiation when you’re off the Earth. Absorption of all those radiations into the Earth’s atmosphere, in the UV, is what starts off the photochemistry of the atmosphere and the whole plethora of problems that come from that. It was relatively simple to make some detectors. Initially we made Lyman-alpha detectors, which were very like the little Geiger counter I had set up – little cylinders with a rod in the middle and a window in the front. By varying the window and the gas we could make detectors which picked out particular bits of the UV.

The very first experiment we did was on the absorption in the atmosphere of Lyman-alpha radiation from the sun. That turned out nicely and gave a rather simple way of measuring the molecular oxygen density profile over a certain range in the atmosphere. The detectors we built for that – again like little versions of Geiger counters – were filled with a gas which provided one limit on the wavelength, and their window in the front could be varied from lithium fluoride or magnesium fluoride right up to quartz and sapphire, providing the other wavelength limit. So they were bandpass devices. We also built lots of ways of testing the detectors, taking a portable UV source up to the range to test them before they were flown in the rocket.

After a number of such experiments in the daylight, mainly getting molecular oxygen, we were very interested in doing similar experiments at night. We had a rather delightful set of experiments which used the full moon as the light source. Out of that we got the reflectivity of the moon in the UV, which was not very well known, and then using that we worked in the peak of the ozone band absorption, about 2500 Ångstroms, and we got ozone distributions at night, high in each tail. One reason for doing that at night was that light has to be very much in photochemical equilibrium and not dominated by transport as the ozone is lower down, particularly during the day.

We spent a few years on this program, doing a lot of experiments but not as many as I would have liked. I always tried to get seasonal and diurnal variations, but we could instrument only about five or six rockets a year – the limit of what the Salisbury people would fire for us. Ideally one would have liked to let off 20 rockets in one day; we never reached that level of power. But we made a lot of the measurements with Brian Rofe's group at WRE and got out a fair amount of data about UV radiation absorption in the Southern Hemisphere.

Not a Woomera failure at all: launching WRESAT 1

In about 1965-66 there was a big Redstone rocket left over from a Woomera program to study re-entry into the atmosphere, and the good-hearted Americans offered it to the Australians who had been working with them, saying that Australia could probably put a satellite in orbit with it. The WRE people at Salisbury said 'yes', and would I be prepared to provide the experimental package? I said of course we would. I knew we had some very good infrastructure as a basis for testing, including a big vacuum tank – big enough to hold the whole satellite – which I had got built with money from the ARC [Australian Research Council]. But after we’d all accepted, the Americans told us we had to do it all in 12 months because then they would have to go home. So Brian Horton and the rest of the university team worked very hard in collaboration with the Salisbury people, and it was all done in 12 months.

As usual I was up there for the launch. Going to launches of rockets is a funny business: most of the people who are there have strong emotional involvement with the rocket but can’t do anything at the time it is to be fired. On the day the rocket was scheduled for firing, the firing schedule went right down to the last minute but then had to be cancelled because things hadn’t worked quite as they should. Everything was put off to the following day and it was very disappointing to go home that night without having fired the rocket. And the press, who all had been there, called it another one of those Woomera failures. By the time we went out the next day, though, the American crew – a pretty tough lot of rednecks – had belted the rocket in a few places and it went off beautifully, with a great roar.

In those early days, 1967, we were the third country to launch our own satellite from our own site. We were front page on every newspaper in Australia. There was a wonderful feeling of delight when it went up. We were able to read the instruments from quite early on in the flight and we could see that everything was working, and then it came round again and you knew it really was in orbit!

Was anyone doing telemetry for you?

Oh yes. Loads of people around the world tracked it for us; we were able to collect data quite continually. And another marvellous thing was that people were so cooperative and friendly about it. Despite all the occasional criticism there has been of Defence Science, when they had this challenging thing to do in a defined time they were wonderful. They would break any rule and do anything to help. If you said you needed batteries to power the thing, and all the paperwork hadn’t gone through, they would nevertheless get them in from the States – and off it went. That was a great thrill and I was very pleased.

Were the scientific results up to what you hoped?

Yes. I would have liked even more data, of course. The flight lasted just a few days at about 200 or 300 kilometres, until eventually its battery power failed and it was brought down by atmospheric drag, doing a re-entry over Ireland.

Focus questions

• How is an understanding of the photochemistry of the atmosphere important to us?

• Why are rockets and satellites used to study the absorption of ultraviolet radiation by the Earth's atmosphere?