INTEGRAL Status Report - November 2006
10 Nov 2006 11:33Mission Status
INTEGRAL operations continue smoothly with the spacecraft, instruments and ground segment performing nominally. 142 proposals were received in response to the 4th Announcement of Opportunity (AO-4) with an over-subscription in time of around 8. In AO-3, 108 proposals were received.
This increase seems to be mainly due to the introduction of a pre-defined Key Programme observation of the galactic bulge region. Due to the large field of views of the INTEGRAL instruments, the observed region of sky includes many individual targets and a total of 43 proposals for sources within the Key Programme field were received.
Operations and Archiving
The 8th SPI annealing was successfully completed on 26 June. The SPI operating temperature was then reduced from 85 K to 82 K in order to reduce the rate of degradation of the instrument's energy resolution caused by radiation. Hopefully this will allow the interval between annealings to be significantly increased from the 6 months currently. In order to mitigate the effects of the increased background counting rate being experienced by SPI due to the changing solar activity, the allocation of telemetry between different SPI data types has been changed to provide additional "headroom" for the primary single events while reducing the allocation given to the (higher energy) multiple events.
The ISDC continues to routinely dispatch data products to observers within 6-8 weeks of their observation. As of September 2006, the on-line ISDC public archive includes nearly all public observations made until July 2005.
The 6th INTEGRAL workshop was held at the Space Research Institute (IKI) in Moscow. The theme was "The Obscured Universe" and the workshop was attended by about 180 scientists from around the world. The topics discussed covered nearly all the major scientific areas being investigated using INTEGRAL, including the nature of the high-energy cosmic background, massive black holes, and nucleosynthesis and X-ray binaries in our own galaxy.
INTEGRAL has detected gamma-ray lines due to the decay of radioactive titanium from the supernova remnant Cassiopeia A which exploded in A.D. 1671. The precise determination of the line flux has enabled the amount of titanium synthesized in the supernova explosion to be reliably measured for the first time. This turns out to be 0.016% of the mass of the Sun, which is much higher than predicted by standard supernovae models. This has led astronomers to propose that Cassiopeia A is a very unusual supernova remnant, perhaps resulting from a very energetic explosion or one which was highly asymmetric.