Re: radioactive debris

Mon, 22 Jan 1996 23:27:51 +0100 (CET)

I hate to boost the volume of SeeSat-L even more (see also a forthcoming
mail on this topic in the next days), but I have to comment on what Leo
Barhorst writes :
>The Lincoln Laboratory's Haystack radar system near Boston supported a
>NASA research in charaterizing the size of space debris. They detected that
>the Cosmos 1900 spacecraft, is leaking coolant (sodium potassium) from its
>nuclear power source. Cosmos 1900, a Radar Ocean Reconnaissance Satellite
>using a nuclear reactor to power its surveillance equipment, was launched
>in december 1987, but suffered a boost problem that left it in a lower than
>planned orbit. One year later the satellite was turned off and transferred
>to a higher orbit.

Rainer Kracht may have been as surprised reading this as I was. Rainer
wrote an article in 'Flash' of April-May 1993 reporting on the flash period
behaviour of Cosmos 1818 (87- 11 A, 17369). The nature of the mission of
this satellite (and its twin sister Cosmos 1867, 87- 60 A, 18187) was unknown,
but similarities with the RORSAT satellites were evident, and by January
1989, soviet scientists confirmed that they were test flights of the TOPAZ
nuclear reactor.

Observers noticed a regular light-variation of Cosmos 1818 in the middle of
May 1992. Bram Dorreman was the first to report a flash period of 5.9 sec.
The rotation of the satellite accelerated continuously until a flash
period of 3.6 seconds was reached in September 1993. The acceleration
halted at that point, and the flash period has been steadily rising until
Mike McCants observation of October 1995 which puts it at 4.23 seconds.

As Rainer mentioned in Flash in 1993, 'this kind of behavior is kind of
rare for a payload, so two explanations are probable :
1. left-over fuel is being gassed out by the 'in-orbit maneuvering stage'
2. the reactor is losing gaseous products of radio-active decay.'

These were only speculations at the time, but Leo's message confirms that
option 2 has happened with other TOPAZ reactors, so it seems highly
probable that this reactor was venting radio-active products as well.

Who needs an expensive radar to figure out what happens to satellites ? ;-)

It may be worthwhile to monitor the other reactors for flash period

   Bart De Pontieu <>