Spacecraft Status

Martin Kessler

The spacecraft status is excellent, with all subsystems performing above specifications. The cryogenic system is providing the expected temperatures and the estimated mass flow rate of the boiled-off helium is close to predictions - no dedicated measurements to determine the lifetime have yet been made but it is expected to be well in excess of the nominal 18 months.

Regarding optical performance of ISO , images of point sources have been made with ISOCAM clearly showing the first Airy diffraction ring; the second ring is also visible in some cases.

The pointing system has been shown to have the following performance:

• relative pointing error (effectively, jitter): 0.5 arcsec (2 sigma) as compared to the specification of < 2.7 arcsecs)
• absolute pointing drift: < 0.1 arcsecs per hour as compared to the specification of < 2.8 arcsecs per hour
• absolute pointing error (effectively, blind pointing accuracy): initial estimates from the results of instruments' pointings show that this is around 5 arcsecs (half cone) as compared to the specification of 11.7 arcsecs.
• slew performance is well within expectations and over 1000 slews have already been successfully completed. An initial anomaly with the temperature of the star tracker has had no operational impacts.