IPN STATUS REPORT AS OF September 24, 2007
Ulysses: The GRB experiment is back on. It has been off as part of a planned power-sharing plan. Power-sharing is necessary because the diminishing RTG power must be used to keep the onboard hydrazine above freezing temperature.
Konus-Wind: operating well. Due to budget cuts, however, the average time between data downlinks is ~30 hours (minimum ~5 h, maximum ~59 h). Since the Konus experiment consists of two detectors facing the north and south ecliptic poles, the ecliptic latitude of a GRB can sometimes be determined by comparing the rates of the two detectors. Generally, the accuracy of this determination is of the order of 10 degrees, which is often sufficient to choose between two alternate arrival directions.
Mars Odyssey: HEND is operating well, and data are downlinked about 8 hours/day, every day. The GRS has been brought into the IPN now. MO is in Martian orbit. Because the spacecraft is in a low altitude orbit, a cone of half-angle 64 degrees is blocked to the two detectors. This information can sometimes be used to choose between two alternate arrival directions. It will only be used in the following way, for most bursts: if the burst is detected by an MO experiment, and if an alternate location is Mars-blocked, that location will be eliminated. Non-detection will not generally be used to choose between alternate locations.
HETE-2: operating only sporadically.
SROSS C-2, SZ-2, NEAR, and BeppoSAX have ceased operations.
RHESSI (the Ramaty High Energy Solar Spectroscopic Imager) has been added to the network. RHESSI is in low Earth orbit, and Earth-blocking can be used to eliminate alternate GRB positions. Also, by comparing the count rates in various detectors, a coarse localization can sometimes be obtained. RHESSI data become available within 24 hours, but some quick-look data are also available.
INTEGRAL (SPI-ACS) has been added to the network. INTEGRAL is in an elliptical orbit, so it is not affected by Earth-blocking, but does lose some time at perigee when it passes through the radiation belts. INTEGRAL SPI-ACS data are downlinked continuously and are available almost immediately after a GRB.
Swift: the Burst Alert Telescope has been added to the network.
MESSENGER is enroute to Mercury, and its gamma-ray detector (a 1 liter plastic scintillator which is part of the neutron detector) is on and detecting bursts.
Suzaku: the WAM serves as a GRB detector, and it has been on and detecting bursts since shortly after launch.
AGILE: Super-AGILE and the mini-calorimeter have been added to the network.
The IPN is detecting about 200 bursts/year in its current configuration. It now comprises three distant spacecraft Ulysses, Odyssey, and MESSENGER), so it can produce small, well-defined error boxes when at least two of them detect a burst. GCN Circulars are only being issued for bursts which are considered interesting. However, all the burst data are being analyzed.