The JET-X instrument is a 4.4 m-long X-ray telescope being built by a consortium of groups from Italy and Russia and led by the UK. It is one of an number of instruments that will constitute the payload of a Russian satellite, Spectrum-X. This is planned to be launched on a Proton rocket from Baikonur in late 1996.
JET-X consists of two identical, co-aligned, imaging telescopes, each with an angular resolution of ~20 arcseconds over the energy band 0.3-10keV. Passively cooled CCD detectors match the telescope spatial resolution and provide high spectral resolution. Two identical attitude monitors, co-aligned with the X-ray telescopes, allow the sky coordinates of the X-ray sources being observed to be determined.
Table 1. Characteristics of the JET-X CCDs
CCD Parameter Value
Pixel format on chip 1024 x 768
Image format per pixel (pixels) 512 x 768
Pixel size 27 x 27 microns
Total active depth (epi-layer) 65 microns
Depletion depth 38 microns
Output node gain ~ 4 mV/ electron
Readout noise < 4 electrons rms
Readout rate per pixel 12 microsec
Dark current @ -80 deg.C 0.004/pixel/sec
Image frame time 2.5 sec
Operating Temperature (start-of-life) 180 - 190 K
Serial Charge Transfer Inefficiency < 1 x 10-5 per pixel
Parallel Charge Transfer Inefficiency < 1 x 10-5 per pixel
In-orbit Spectrum-X operations will be run from the Moscow based Russian Space Research Institute (IKI). Spectrum-X will be placed in a highly elliptic, 200,000km apogee, 51.5 deg. inclination, 4-day orbit giving long contact periods with the Moscow ground station that will provide the telemetry link to the spacecraft.
JET-X will be run as an observatory so that UK astronomers will be able to bid for observations to be made during the UK share of observing time. Part of IKI's responsibility will be to assemble the 6-month, or possibly 1 year, observing programmes that will constitute the Spectrum-X mission. Nominally, up to ~ 15 pointings can be carried during a given 4-day orbit period.
A JET-X Ground System is being developed to provide the UK input to the overall observing programmes, monitor instrument health and performance and transfer and pre-process JET-X data from IKI to UK Guest Observers. Four institutes, Birmingham University (BU), Leicester University (LU), the Mullard Space Science Laboratory (MSSL) and the Rutherford Appleton Laboratory (RAL) share ground system development tasks. MSSL will be largely responsible for a Quick Look Facility at IKI which will provide the JET-X interface to the Spectrum-X planning and operations systems. The QLF will also transfer JET-X data to a data centre at RAL. This will pre-process observations data into FITS format data sets and distribute them to UK Guest Observers. An Instrument Analysis Centre, based at LU, will analyse calibration data and maintain the calibration files, the IAC will also monitor detailed instrument performance. The Announcement of Opportunity, Guest Observer support, and analysis software system are responsibilities shared between LU and BU.