[X] My Assistant

[PhilHorzempa]

SEASAT was a pioneering mission in using SAR to produce images of
a planetary surface. It was the true precursor mission that made Magellan,
the SRTM (STS-99), and Cassini possible.

It was launched in 1978 and its mission was relativley short.
Even though its main mission was monitoring sea surface conditions, its SAR
produced a good number of high-quality images of the continents.

Does anyone in the UMSF community have good Earth images from SEASAT
that they could share? Those images seem to be scarce on the Internet.
Also, images of the SEASAT spacecraft itself would be neat to see.


Another Phil

[dvandorn]

The Agena was originally developed as an upper stage that would serve as the foundation for the early Keyhole (or KH) spy satellites, but it was used from the outset as a generic upper stage for the Atlas rocket. Not only was it the upper stage of choice for many satellites and planetary probes throughout the early and mid 1960s, it also served as the rendezvous target for Gemini spacecraft.

IIRC, the Agena was the first three-axis-stabilized upper stage developed by the U.S. That made it quite in demand for planetary probes (which, at the time, you didn't want to put into a spin prior to escape trajectory injection), as well as for any satellite that you wanted three-axis-stabilized but didn't want to spend the time and money to develop an RCS for... This was a requirement for the early KH series, but it was a happy circumstance for a whole generation of spacecraft designers.

As for SEASAT in particular, I don't believe it was primarily an NRO type of mission. Yes, a lot of the SAR flown by the U.S. has been NRO-related (primarily to get good ground elevation maps for cruise missile navigation), but SEASAT itself was, IIRC, for scientific research. It's easy to confuse this, since the USSR flew a lot of oceanic radar surveillance spacecraft whose jobs were to track U.S. naval movements (including, it was hoped, shallow submarine assets). The Russian SAR required so much power that they flew with actual fission-pile nuclear reactors; it was one of these that crashed onto Canada, spreading nuclear material over the countryside. American SAR missions have used solar energy (or, in the case of the Shuttle-borne SAR, fuel cell-generated power).

-the other Doug