Telstar I was launched on July 10, 1962. That evening, beginning on the
satellite’s seventh pass, we were able to detect trains of flashes from
the mirrors. We assumed that, since Telstar had been launched almost
exactly according to plan, its spin axis would be perpendicular to the
plane of the earth’s orbit, and we calculated when we should see the
flashes. And, each time, we actually saw them within two minutes of the
times we had predicted—so we knew that the spin axis was almost exactly
where it should be.
Our measurements have continued whenever the weather and other
conditions permitted. Combining readings from the bursts of flashes and
telemetry data from the solar aspect cells, we have accurately plotted
Telstar’s spin axis; it has continued to precess very much as we
predicted it would. We have also seen what happens to the spin axis when
the satellite’s torque coil is turned on. And, by measuring the
intervals between flashes, we have made very precise measurements of the
spin rate, which is gradually decreasing mostly according to schedule.
However, the plot is showing some small unexplained variations of spin
decay rate, and a study of them will, we hope, throw light on some of
the variations of the earth’s magnetic field.
For future communications work, particularly with satellites at longer
ranges, it would seem to be preferable to use stiffer, flatter mirrors
and to make them from beryllium rather than aluminum alloy. More
accurate tracking means, more observatory sites, and more powerful
telescopes will also be needed. But for this first experimental use our
little mirrors have worked very well.
Jeofry S. Courtney-Pratt _was born in Hobart, Tasmania, Australia, and
received a Bachelor of Engineering degree from the University of
Tasmania in 1942 and a Ph.D. from Cambridge University in 1949. He was
also awarded an Sc.D. by Cambridge in 1958. He joined Bell Telephone
Laboratories in 1958, and has done research in high-speed photography,
optics, optical masers, the properties of materials, and the physics
of the contact of solids._
CASE HISTORY NO. 4
How Do We Keep Solar Cell Power Plants Working in Space?
Kenneth D. Smith
_Electronics Engineer—Member of Staff, Semiconductor Device Laboratory_