ESA Science & Technology - Publication Archive

Workshop held 22-25 June 1999 in Paris, France.

Proc. Kanzelhoehe Summer School, eds. A. Hanslmeier and M. Messerotti, Kluwer, 2001

Kosovichev, A.G., Duvall, T.L. (eds.)

The spectrometer on INTEGRAL (SPI) is one of the two main telescopes of the future INTEGRAL observatory. SPI is made of a compact hexagonal matrix of 19 high-purity germanium detectors shielded by a massive anticoincidence system. A HURA type coded aperture modulates the astrophysical signal. The spectrometer system, its physical characteristics and performances are presented. The instrument properties such as imaging capability, energy resolution and sensitivity have been evaluated by means of extensive Monte-Carlo simulations. With the expected performances of SPI, it will be possible to explore the gamma-ray sky in greater depth and detail than it was possible with previous gamma-ray telescopes like SIGMA, OSSE and COMPTEL. In particular, the high-energy resolution will allow for the first time the measurement of gamma-ray line profiles. Such lines are emitted by the debris of nucleosynthesis and annihilation processes in our Galaxy. Lines from these processes have already been measured, but due to the relatively poor energy resolution, details of the emission processes in the source regions could not be studied. With the high-resolution spectroscopy of SPI such detailed investigations will be possible.

The International Gamma-Ray Astrophysics Laboratory (INTEGRAL), to be launched in 2001, is dedicated to the fine spectroscopy (DE: 2 keV FWHM @ 1.3 MeV) and fine imaging (angular resolution: 12' FWHM) of celestial gamma-ray sources in the energy range 15 keV to 10 MeV with concurrent source monitoring in the X-ray (3-35 keV) and optical (V, 550 nm) range. The mission is conceived as an observatory led by ESA with contributions from Russia and NASA. The INTEGRAL observatory will provide to the science community at large an unprecedented combination of imaging and spectroscopy over a wide range of gamma-ray energies. This paper summarises the key scientific goals of the mission, the current development status of the payload and spacecraft and it will give an overview of the science ground segment including the science data center, science operations and key elements of the observing program.

SUMER - the Solar Ultraviolet Measurements of the Emitted Radiation instrument on the Solar and Heliospheric Observatory (SOHO) - observed its first light on January 24, 1996, and subsequently obtained a detailed spectrum with detector B in the wavelength range from 660 to 1490 Å (in first order) inside and above the limb in the north polar coronal hole. Using detector A of the instrument, this range was later extended to 1610 Å. The second-order spectra of detectors A and B cover 330 to 805 Å and are superimposed on the first-order spectra. Many more features and areas of the Sun and their spectra have been observed since, including coronal holes, polar plumes and active regions. The atoms and ions emitting this radiation exist at temperatures below 2 ×106 K and are thus ideally suited to investigate the solar transition region where the temperature increases from chromospheric to coronal values. SUMER can also be operated in a manner such that it makes images or spectroheliograms of different sizes in selected spectral lines. A detailed line profile with spectral resolution elements between 22 and 45 mÅ is produced for each line at each spatial location along the slit. From the line width, intensity and wavelength position we are able to deduce temperature, density, and velocity of the emitting atoms and ions for each emission line and spatial element in the spectroheliogram. Because of the high spectral resolution and low noise of SUMER, we have been able to detect faint lines not previously observed and, in addition, to determine their spectral profiles. SUMER has already recorded over 2000 extreme ultraviolet emission lines and many identifications have been made on the disk and in the corona.

SOHO, launched by an Atlas II-AS from Cape Canaveral on 2 December 1995, was inserted into its halo orbit around the L1 Lagrangian point on 14 February, six weeks ahead of schedule. The launch and the orbital manoeuvres were so accurate and efficient that sufficient fuel remains on board to maintain the halo orbit for more than a decade, i.e. for at least twice as long as originally foreseen. Already during their commissioning phase, the SOHO experiments have returned a wealth of data, impressive in terms of both its quality and diversity. Some of the images can be viewed via the SOHO pages (http://sohowww.nascom.nasa.gov) on the World Wide Web, and on the individual experiment pages, all with links from the SOHO home page. Typical examples of the unique results being obtained with SOHO's instruments are presented here. Although they have been obtained with single instruments, it is worth noting that the main scientific advances from SOHO are expected to come from the joint analysis of coordinated observations.

Proceedings of the 3rd INTEGRAL Workshop, Taormina 1998

The INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL) is being developed by ESA as the second medium-size satellite of the long-term scientific plan Horizon 2000. It is an observatory providing an excellent opportunity to the scientific community for detailed imaging and high-resolution spectroscopy of Gamma-ray sources.
After completion of the design and development phase the Structural Thermal Model of the Integral Spacecraft and its four scientific instruments is presently being tested. First tests took place in spring 1998 at the ESTEC test facilities. Late summer 1998 the Engineering Model test campaign will follow.
This paper summarises the key programmatic milestones of the project, highlights the final design characteristics of the satellite, reports on the first test results, and describes the orbital scenario of the mission and the herewith-related requirements to the satellite.

A couple years ago researchers announced that they had discovered traces of water on the sun. A team at Stanford University has just gone them one better, discovering entire rivers on the sun. These are not rivers in the familiar sense, of course; rather they are huge, snaking flows within the white-hot plasma (electrically charged gas) that makes up the sun.

COBRAS/SAMBA: Report on the Phase A Study, ESA D/SCI (96)3, 1996,

(Note that at the time the Study was written, the Planck project was still referred to as COBRAS/SAMBA, so you will find the latter name extensively used.)

The in-orbit imaging performance of the three X-ray telescopes on board of the X-ray astronomy observatory XMM-Newton is presented and compared with the performance measured on ground at the MPE PANTER test facility. The comparison shows an excellent agreement between the on ground and in-orbit performance.

The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is dedicated to the fine spectroscopy (Delta-E: 2 keV FWHM @ 1.3 MeV) and fine imaging (angular resolution: 12 arcmin FWHM) of celestial gamma-ray sources in the energy range 15 keV to 10 MeV with concurrent source monitoring in the X-ray (3 - 35 keV) and optical (V, 550 nm) range. The mission is conceived as an observatory led by ESA with contributions from Russia and NASA. The INTEGRAL observatory will provide to the science community at large an unprecedented combination of imaging and spectroscopy over a wide range of energies. Most of the observing time will be open to the scientific community. This paper summarises the key scientific goals of the mission, the current development status of the payload and spacecraft and it will give an overview of the science ground segment including data centre, science operations and the key elements of the observing programme

Gamma Ray Burst (GRB) afterglows close to their peak intensity are among the brightest X-ray sources in the sky. Despite their fast power-law like decay, when fluxes are integrated from minutes up to hours after the GRB event, the corresponding number counts (logN-logF relation) far exceeds that of any other high redshift (z>0.5) source, the flux of which is integrated over the same time interval. We discuss how to use X-ray afterglows of GRBs as distant beacons to probe the warm (10⁵ K7 K) intergalactic matter in filaments and outskirts of clusters of galaxies by means of absorption features, the "X-ray forest''. According to current cosmological scenarios this matter may comprise 30-40% of the baryons in the Universe at z<1. Present-generation X-ray spectrometers such as those on Chandra and XMM-Newton can detect it along most GRBs' lines of sight, provided afterglows are observed fast enough (within hours) after the burst.

The Core Programme of the INTEGRAL mission is defined as the portion of the scientific programme covering the guaranteed time observations for the INTEGRAL Science Working Team. This paper describes the current status of the Core Programme preparations and summarizes the key elements of the observing programme. Letters & Communications, 1999