Jacques van Oene
November 29th 04, 10:14 PM
INTEGRAL Status Report - November 2004
29 Nov 2004 16:06
Mission Status
INTEGRAL operations continue smoothly with the spacecraft, instruments and
ground segment performing well. Two of the instruments have had anomalies
recently. The third INTEGRAL Announcement of Opportunity for observing
proposals (AO-3) opened on 13 September 2004. The AO covers observations
between 18 February 2005 and 17 August 2006 and the results will be known in
December 2004. Preparations for the move of the INTEGRAL Science Operations
Centre (ISOC) from ESTEC to the ESAC continue.
Operations and Archiving
Shortly before the expected loss of signal due to perigee passage on 2 June,
the imager (IBIS) digital electronics stopped responding to commands. Since
the IBIS high-voltages (HV) were still on, passage through the radiation
belts would have degraded the photo-multiplier tubes of the veto sub-system.
Within the 10 minutes available before loss of signal, the Mission Operation
Centre (MOC) team correctly analysed the situation and turned off the power
to the IBIS peripherals. The problem has not recurred. There were 6 resets
of the INTEGRAL Radiation Monitor (IREM) during the summer resulting in the
instruments being put into safe-mode/stand-by for a few hours each time. The
anomalies are still under investigation and the most probably cause is
single event upsets of the RAM by heavy cosmic-ray particles.
The 4th spectrometer (SPI) annealing was successfully completed on 30 June
with a full recovery of the pre-launch energy resolution. However, SPI
detector #17 failed on 17 July (2 out of 19 detectors are now off) and
attempts to recover it have been unsuccessful. To first order, these
failures decrease the SPI efficiency by ~10%. It is yet unclear whether the
failures are linked to the annealing which preceded the failures in both
cases. The failures are most probably in the detector pre-amplifiers, HV
power supplies or associated cabling. The instrument team is conducting
ground tests using flight spare hardware to see it the failures can be
replicated. ESA is supporting these activities with computer modeling. The
INTEGRAL Science Working Team will be asked to recommend on future annealing
strategy.
The fourth release of the INTEGRAL Science Data Centre (ISDC) public
off-line scientific analysis (OSA) software took place in July. This release
includes a number of improved data analysis tools that allow for example,
better modeling of off-axis sources, as well as improved spectral response
matrices. The ISDC continues to routinely dispatch data products to
observers within 6-8 weeks of their observation. The first INTEGRAL
observations entered the public domain on 17 July 2004 and are made
available to the scientific community via the on-line ISDC archive.
Currently, observations from approximately the first 8 months of
observations are publicly available. The ISDC has also put a bright source
catalog on-line (http://isdc.unige.ch/index.cgi?Data+sources). This contains
science products from the Imager and Spectrometer (light-curves and fluxes
in different energy bands) for the ~70 brightest INTEGRAL sources. It is
regularly updated as more data is added to the public archive.
Science Highlights
Results from the INTEGRAL survey showed very hard emission from a region
including the anomalous X-ray pulsar (AXP) 1E 1841-045 (Molkov et al,
astro-ph/040216). AXPs are thought to be neutron stars where the high-energy
emission is powered by an intense magnetic field - hence these sources being
referred to as "magnetars". Triggered by the INTEGRAL survey result, Kuiper
et al. (ApJ in press) examined R-XTE and XMM-Newton observations of 1E
1841-045 and reported the surprising discovery that the source has an
extremely hard spectrum extending to ~150 keV. This was totally unexpected
since previous studies of AXPs had revealed only extremely soft spectra. The
discovery has major implications on the emission mechanisms of AXPs, their
relation to soft gamma-ray repeaters and to the un-identified EGRET sources.
The INTEGRAL-discovered GRB 031202 turned out to be the closest and faintest
gamma-ray burst (GRB) observed so far. Two papers in the August issue of
Nature (Sazonov et al., vol. 430, p. 646, and Soderberg et al. vol. 430, p.
648) address the nature of this intrinsically sub-energetic event. Its
luminosity is comparable to only one other GRB (GRB 980425) observed so far
and it is possible that these represent a yet unknown GRB population of very
faint events. Finally, by combining INTEGRAL and XMM-Newton observations of
a nearby Seyfert galaxy NGC 4388, Beckmann et al. (ApJ in press) have found
further evidence that doughnut-shaped gas and dust clouds surround massive
black holes. These discoveries were the topics of two ESA Science News
Releases (SNR-16-2004 and SNR-18-2004).
--
--------------
Jacques :-)
www.spacepatches.info
29 Nov 2004 16:06
Mission Status
INTEGRAL operations continue smoothly with the spacecraft, instruments and
ground segment performing well. Two of the instruments have had anomalies
recently. The third INTEGRAL Announcement of Opportunity for observing
proposals (AO-3) opened on 13 September 2004. The AO covers observations
between 18 February 2005 and 17 August 2006 and the results will be known in
December 2004. Preparations for the move of the INTEGRAL Science Operations
Centre (ISOC) from ESTEC to the ESAC continue.
Operations and Archiving
Shortly before the expected loss of signal due to perigee passage on 2 June,
the imager (IBIS) digital electronics stopped responding to commands. Since
the IBIS high-voltages (HV) were still on, passage through the radiation
belts would have degraded the photo-multiplier tubes of the veto sub-system.
Within the 10 minutes available before loss of signal, the Mission Operation
Centre (MOC) team correctly analysed the situation and turned off the power
to the IBIS peripherals. The problem has not recurred. There were 6 resets
of the INTEGRAL Radiation Monitor (IREM) during the summer resulting in the
instruments being put into safe-mode/stand-by for a few hours each time. The
anomalies are still under investigation and the most probably cause is
single event upsets of the RAM by heavy cosmic-ray particles.
The 4th spectrometer (SPI) annealing was successfully completed on 30 June
with a full recovery of the pre-launch energy resolution. However, SPI
detector #17 failed on 17 July (2 out of 19 detectors are now off) and
attempts to recover it have been unsuccessful. To first order, these
failures decrease the SPI efficiency by ~10%. It is yet unclear whether the
failures are linked to the annealing which preceded the failures in both
cases. The failures are most probably in the detector pre-amplifiers, HV
power supplies or associated cabling. The instrument team is conducting
ground tests using flight spare hardware to see it the failures can be
replicated. ESA is supporting these activities with computer modeling. The
INTEGRAL Science Working Team will be asked to recommend on future annealing
strategy.
The fourth release of the INTEGRAL Science Data Centre (ISDC) public
off-line scientific analysis (OSA) software took place in July. This release
includes a number of improved data analysis tools that allow for example,
better modeling of off-axis sources, as well as improved spectral response
matrices. The ISDC continues to routinely dispatch data products to
observers within 6-8 weeks of their observation. The first INTEGRAL
observations entered the public domain on 17 July 2004 and are made
available to the scientific community via the on-line ISDC archive.
Currently, observations from approximately the first 8 months of
observations are publicly available. The ISDC has also put a bright source
catalog on-line (http://isdc.unige.ch/index.cgi?Data+sources). This contains
science products from the Imager and Spectrometer (light-curves and fluxes
in different energy bands) for the ~70 brightest INTEGRAL sources. It is
regularly updated as more data is added to the public archive.
Science Highlights
Results from the INTEGRAL survey showed very hard emission from a region
including the anomalous X-ray pulsar (AXP) 1E 1841-045 (Molkov et al,
astro-ph/040216). AXPs are thought to be neutron stars where the high-energy
emission is powered by an intense magnetic field - hence these sources being
referred to as "magnetars". Triggered by the INTEGRAL survey result, Kuiper
et al. (ApJ in press) examined R-XTE and XMM-Newton observations of 1E
1841-045 and reported the surprising discovery that the source has an
extremely hard spectrum extending to ~150 keV. This was totally unexpected
since previous studies of AXPs had revealed only extremely soft spectra. The
discovery has major implications on the emission mechanisms of AXPs, their
relation to soft gamma-ray repeaters and to the un-identified EGRET sources.
The INTEGRAL-discovered GRB 031202 turned out to be the closest and faintest
gamma-ray burst (GRB) observed so far. Two papers in the August issue of
Nature (Sazonov et al., vol. 430, p. 646, and Soderberg et al. vol. 430, p.
648) address the nature of this intrinsically sub-energetic event. Its
luminosity is comparable to only one other GRB (GRB 980425) observed so far
and it is possible that these represent a yet unknown GRB population of very
faint events. Finally, by combining INTEGRAL and XMM-Newton observations of
a nearby Seyfert galaxy NGC 4388, Beckmann et al. (ApJ in press) have found
further evidence that doughnut-shaped gas and dust clouds surround massive
black holes. These discoveries were the topics of two ESA Science News
Releases (SNR-16-2004 and SNR-18-2004).
--
--------------
Jacques :-)
www.spacepatches.info