Posted on 11/06/2002 9:38:59 AM PST by Stand Watch Listen
China launched the second in its Zi Yuan-2 (ZY-2) series of photo-reconnaissance satellites from the Tai Yuan centre on 27 October using a CZ-4B launch vehicle. The first ZY-2 satellite was launched on 1 September 2000.The approximately 1.5 tonnes ZY-2 satellite is the military version of the ZY-1/China Brazil Earth Resource Satellite (CBERS) platform that China developed jointly with Brazil for use as a civilian remote-sensing satellite. The ZY-1 version has an advertised operational lifetime of two years and it would be reasonable to assume that the military version has the same planned lifetime.
The first ZY-2 satellite operates in a 490-495km orbit, much lower than the ZY-1/CBERS (about 774km). This has the advantage that higher-resolution images can be obtained if CBERS-class imaging systems are carried; if higher-performance military systems are used then the ground resolution should be in the range of 10-20cm. The disadvantage of the lower orbit is that more frequent orbital corrections are required (the most recent one on 24 October) to counter the greater effects of orbital decay. As a result, the operational lifetimes of ZY-2 satellites will probably be limited more by the propellant mass carried, rather than the longevity of the on-board instrumentation.
The new ZY-2 satellite was launched into an approximately 475-495km orbit (US Space Command's initial orbital data suggests a more eccentric orbit, but this is probably because its initial data was inaccurate as the third stage of the CZ-4B launcher is in the 'right' orbit). If the pattern of the first satellite is followed it will manoeuvre to its operational orbit within 10 days of its launch. After that, one to two orbit maintenance manoeuvres will be required each month - raising the orbit by 4km each time - to counter the effects of atmospheric drag.
Like CBERS for the ZY-1 series of satellites, the ZY-2 series has the 'classified' name Jian Bing-3 (JB, 'pathfinder') within Chinese circles. The designators JB-1, -2A and -2B were applied to China's Fanhui Shi Weixing (FSW) series of recoverable satellites. Some analysts have suggested that all of the FSW satellites had JB designators, but this is incorrect. The JB designator is reserved only for satellites that are used primarily for photo-reconnaissance operations. ZY-2/JB-3 satellites are not recoverable.They return their data via digital link like the ZY-1/CBERS satellites and they are, therefore, not limited by having to carry a fixed reserve of photographic film.
If they had any gratitude at all they'd name it the Bill Clinton.
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