The XMM-Newton observatory, launched by the European Space Agency in 1999, is still one of the scientific community’s most important high-energy astrophysics missions. After almost 15 years in orbit its instruments continue to operate smoothly with a performance close to the immediate post-launch status. The competition for the observing time remains very high with ESA reporting a very healthy over-subscription factor. Due to the efficient use of spacecraft consumables XMM-Newton could potentially be operated into the next decade. However, since the mission was originally planned for 10 years, progressive ageing and/or failures of the on-board instrumentation can be expected. Dealing with them could require substantial changes of the on-board operating software, and of the command and telemetry database, which could potentially have unforeseen consequences for the on-board equipment. In order to avoid this risk, it is essential to test these changes on ground, before their upload. To this aim, two flight-spare cameras of the EPIC experiment (one MOS and one PN) are available on-ground. Originally they were operated through an Electrical Ground Support Equipment (EGSE) system which was developed over 15 years ago to support the test campaigns up to the launch. The EGSE used a specialized command language running on now obsolete workstations. ESA and the EPIC Consortium, therefore, decided to replace it with new equipment in order to fully reproduce on-ground the on-board configuration and to operate the cameras with SCOS2000, the same Mission Control System used by ESA to control the spacecraft. This was a demanding task, since it required both the recovery of the detailed knowledge of the original EGSE and the adjustment of SCOS for this special use. Recently this work has been completed by replacing the EGSE of one of the two cameras, which is now ready to be used by ESA. Here we describe the scope and purpose of this activity, the problems faced during its execution, the adopted solutions, and the tests performed to demonstrate the effectiveness of the new EGSE.
The Energetic X-ray Imaging Survey Telescope (EXIST) mission, submitted to the Decadal Survey, is a
multiwavelength observatory mainly devoted to the study of Super Massive Black Holes, Gamma Ray Bursts and other
transient sources. The set of instruments foreseen for EXIST includes a soft x-ray telescope (SXI), proposed as a
contribution of the Italian Space Agency (ASI).
We present the baseline design of the X-Ray camera for SXI telescope, that we have finalized under ASI contract. The
camera is based on a focal plane detector consisting of a 450 μm thick silicon pixel sensor sensitive, with high QE, in the
full SXI range (0.1-10 KeV), and capable of high energy resolution when operated in photon counting mode (E/dE ~ 47
at 6 keV), frame rate ~ 100-200 frames/s (enabling timing in the ms range), and spatial resolution matching the optical
characteristics of the mirror module. We provide an overview of the mechanical, thermal and electrical concept of the
The Energetic X-ray Imaging Survey Telescope (EXIST) will continuously survey the full sky in scanning mode for 2-
years followed by a 3-years pointing phase. The mission includes three instruments: a High Energy coded mask
Telescope; a 1.1m aperture optical-IR Telescope; and a Soft X-ray Imager (SXI), sensitive in the 0.1-10 keV band. SXI
is proposed as a contribution of ASI-Italy, fully developed by Italian institutes. Here we will present the optical and
mechanical design of the SXI mirror module, that includes also a pre-collimator and a magnetic diverter to ensure a low
background on the detector. In particular we will describe the mirror module characteristics in term of effective area,
imaging capability, thermal requirement and mechanical properties. The current optical design foresees 26 shells
providing an effective area comparable to one XMM-Newton mirror module up to 3 keV. The realization of these shells
is based on the well-proven Nickel replication-process technology.
The New Hard X-ray Mission (NHXM) has been designed to provide a real breakthrough on a number of hot
astrophysical issues that includes: black holes census, the physics of accretion, the particle acceleration mechanisms, the
effects of radiative transfer in highly magnetized plasmas and strong gravitational fields. NHXM combines fine imaging
capability up to 80 keV, today available only at E<10 keV, with sensitive photoelectric imaging polarimetry. It consists
of four identical mirrors, with a 10 m focal length, achieved after launch by means of a deployable structure. Three of the
four telescopes will have at their focus identical spectral-imaging cameras, while a X-ray imaging polarimeter will be
placed at the focus of the fourth. In order to ensure a low and stable background, NHXM will be placed in a low Earth
equatorial orbit. Here we will provide an overall description of this mission and of the developments that are currently
occurring in Italy. In the meanwhile we are forming an international collaboration, with the goal to have a consortium
of leading Institutes and people that are at the forefront of the scientific and technological developments that are
relevant for this mission.
NHXM, under study by ASI (Agenzia Spaziale Italiana), is an X-ray observatory in the energy band between 0.5 and
80 keV and will have 3 telescopes dedicated to X-ray imaging with a field of view diameter of 12 arcmin and a focal
length of 10 m. We report on the development of high-speed and low-noise readout of a monolithic array of DEPFET
detector. The DEPFET based detectors, thanks to an intrinsic low anode capacitance, are suitable as low-energy
detectors (from 0.5 to 10 keV) of the new NHXM telescope.
The challenging requirements of the NHXM cameras regard the necessity to obtain images and spectra with
nearly Fano-limited energy resolution with an absolute time resolution of about 100 μs. In order to exploit the speed
capability of the DEPFET array, it has been developed a readout architecture based on the VELA circuit: a drain
current readout configuration to implement an extremely fast readout (2 μs/row) and preserve the excellent noise
performance of the detector.
In the paper the foreseen maximum achievable frame-rate and the best energy resolution will be presented in
order to assert the VELA suitability for X-ray imaging and spectroscopy.
The New Hard X-ray Mission (NHXM) is conceived to extend the grazing-angle reflection imaging capability up to
energy of 80 keV. The NHXM payload consists of four telescopes. Three of them have at their focal plane identical
spectral-imaging camera operating between 0.2 and beyond 80 keV, while the fourth has a X-ray imaging polarimeter.
The spectral-imaging cameras are constituted by two detection layers: a Low Energy Detector (LED) and a High Energy
Detector (HED) surrounded by an Anti Coincidence (AC) system. Here we will present the preliminary design and the
solutions that we are currently studying to meet the top level system requirements of these cameras.
The Energetic X-ray Imaging Survey Telescope (EXIST) is a mission that has been studied for the NASA Physics of the
Cosmos Program. EXIST will continuously survey the full sky by scanning for 2-years (with 2-3 interruptions per day
for GRB follow-up) followed by a 3-years pointing phase. The mission includes three instruments: a High Energy coded
mask Telescope; a 1.1m aperture optical-IR Telescope; and a Soft X-ray Imager (SXI), sensitive in the 0.1-10 keV band.
SXI is proposed as a contribution of ASI-Italy, fully developed by Italian institutes. The current optical design foresees
26 shells providing an effective area comparable to one XMM-Newton mirror module up to 3 keV and somewhat lower
from 3 to 10 keV. The realization of these shells is based on the well-proven Nichel replication-process technology. Here
we will present the optical design of the SXI mirror module and describe its characteristics in term of effective area and
imaging capability, summarizing also the characteristics of the full SXI telescope.
The SXI telescope is one of the three instruments on board EXIST, a multiwavelenght observatory in charge of
performing a global survey of the sky in hard X-rays searching for Supermassive Black Holes. One of the primary
objectives of EXIST is also to study with unprecedented sensitivity the most unknown high energy sources in
the Universe, like high redshift GRBs, which will be pointed promptly by the Spacecraft by autonomous trigger
based on hard X-ray localization on board. The recent addition of a soft X-ray telescope to the EXIST payload
complement, with an effective area of 950 cm<sup>2</sup> in the energy band 0.2-3 keV and extended response up to 10 keV
will allow to make broadband studies from 0.1 to 600 keV. In particular, investigations of the spectra components
and states of AGNs and monitoring of variability of sources, study of the prompt and afterglow emission of GRBs
since the early phases, which will help to constrain the emission models and finally, help the identification of
sources in the EXIST hard X-ray survey and the characterization of the transient events detected. SXI will also
perform surveys: a scanning survey with sky coverage ~ 2 π and limiting flux of ~ 5 × 10<sup>-14</sup> cgs plus other
serendipitous. We give an overview of the SXI scientific performance and also describe the status of its design
emphasizing how it has been derived by the scientific requirements.
We are conducting a measurement program on back-up filters of the
XMM-Newton EPIC camera aimed at monitoring possible aging effects
during the mission lifetime. One thin and one medium EPIC back-up
filters have been stored since 1997 in an environment similar to that
one of the flight filters (dry nitrogen box before launch, high vacuum
after launch). The transmission of the two filters has been measured
periodically in the 1900-10000 angstrom wavelength range where effects of aging would be clearly evident. The preliminary results, after 5 years of monitoring, show that a slight aging effect has occurred on both filters which, however, has no significant impact onto the EPIC calibration for the correct analysis of the X-ray astrophysical observations.
EPIC, on the Newton Observatory, comprises three CCD cameras that provide spectroscopic imaging over the band 0.1-12 keV, with full coverage of the 30' diameter field of view of the three telescopes. The combination of bandwidth, throughput, and spectral resolution, has produced many interesting observations in more than two years of operation. These range from stars, normal, and neutron, SNR & Pulsars, via galaxies, to clusters of galaxies and the most distant quasars. Some of the latest results will be presented. A few days' operation on orbit provides more instrument performance data that can be gathered in the most thorough ground calibration, and many new facets of the instrument performance become evident in orbit. The high throughput of the Newton telescopes provides images and spectra of high statistical precision. This puts an additional burden on the calibration, and there has been much progress by the EPIC team in defining a precise and accurate calibration at the few percent level. The EPIC MOS CCDs perform well in orbit and show considerable radiation hardness against soft protons, due to their peculiar architecture. The degradation of spectral resolution, due to radiation damage, is dominated by hard solar flare protons. At present, this is within the predicted limits and the good spectral performance of EPIC is maintained.
A Mission into Hot Phenomena in the Universe is proposed by means of a small telescope of 50 cm aperture accommodated on the International Space Station. Two operating modes are envisaged: 3 angstrom dispersion imaging spectroscopy in the 90 - 320 nm range (1st priority) or wide field (1 degree) medium bandwidth imaging in the same range but Ly-(alpha) (2nd priority). It will use a pointing platform attached to an Express Pallet Adapter available to the Italian Space Agency (ASI) more than 4 - 6 months per year. During a life time of 6 yr focal plane instruments may be changed when on-ground refurbishment occurs. With reasonable exposure times hot thermal sources as faint as V equals 19 - 2 can be observed in the spectroscopy mode at 110 nm and active chromospheres on cool stars as faint as V equals 15 at 250 nm can be monitored. Assessment of FUV imaging is underway, possibly providing observations of hot sources as faint as V equals 21 - 22. Nominal uplift to ISS is set in Autumn 2005.
The combined effective area of the three EPIC cameras of the XMM-Newton Observatory, offers the greatest collecting power ever deployed in an X-ray imaging system. The resulting potential for high sensitivity, broad-band spectroscopic investigations demands an accurate calibration. This work summarizes the initial in-orbit calibration activities that address these requirements. We highlight the first steps towards effective area determination, which includes the maintenance of gain CTI calibration to allow accurate energy determination. We discuss observations concerning the timing and count-rate capabilities of the detectors. Finally we note some performance implications of the optical blocking filters.
On 10th December 1999, the European X-ray satellite XMM, now called XMM-Newton, was successfully put into orbit. After initial commissioning of the satellite's subsystems, the EPIC-pn camera was switched on and tested thoroughly in the period Jan./Febr. 2000. After refining of some of the parameter settings and the on-board pn-computer programs, we started the Calibration and Performance Verification Phase, which will last until the end of May 2000. In this paper we report on the results of the EPIC-pn Commissioning Phase with respect to the in-orbit performance of the camera. We also show some of the early results with the pn-camera, the first light image of a region in the Large Magellanic Cloud, and an observation of the Crab Nebular.
The European photon imaging camera (EPIC) is one of the two main instruments onboard the ESA X-Ray Cornerstone Mission XMM. It is devoted to performing imaging and spectroscopy of the x-ray sky in the domain 0.1 10 keV with a peak sensitivity in 10<SUP>5</SUP> seconds of 2 multiplied by 10<SUP>-15</SUP> erg/cm<SUP>-2</SUP>. The x-ray instrumentation is complemented by a radiation monitor which will measure the particle background. The spectral resolution is approximately 140 eV at 6.4 keV and 60 eV at 1 keV. The instrumentation consists of three separate focal plane cameras at the focus of the three XMM telescopes, containing CCDs passively cooled to typically minus 100 degrees via radiators pointing toward the anti-Sun direction. The two cameras with the field of view partially occulted by the RGS grating boxes will have MOS technology CCDs while the third camera, with full field of view, will be based on p-n technology. The CCDs in the focal plane of the cameras will cover the entire 30 foot by 30 foot field of view of the telescope while the pixel size (40 by 40 (mu) for the MOS camera and 150 multiplied by 150 (mu) for the p-n) will be adequate to sample the approximately 20' PSF of the mirrors. In order to cope with a wide range of sky background and source luminosity in the visible/UV band, a filter wheel with six positions has been implemented in each camera. The six positions correspond to: open position, closed position, one thin filter (1600 angstrom of plastic support and 400 angstrom of Al), one medium filter (1600 angstrom of plastic support and 800 angstrom of Al) and one thick filter (approximately 3000 angstrom of plastic support, approximately 1000 angstrom of Al and 300 Angstrom of Sn). The final position will be a redundant filter of type still to be decided. A set of radioactive sources in each camera will allow the calibration of the CCDs in any of the operating modes and with any filter wheel position. Vacuum doors and valves operated will allow the operation of other camera heads on the ground, in a vacuum chamber and/or in a controlled atmosphere, and will protect the CCDs from contamination until the spacecraft is safely in orbit. The MOS camera will have 7 CCDs, each of 600 by 600 pixels arranged in a hexagonal pattern with one central and six peripheral. The p-n camera head will have 12 CCDs, each with 200 multiplied by 64 pixels, in a rectangular arrangement, 4 quadrants of 3 CCDs each. The radiation monitor is based on two separate detectors to monitor the low (electrons greater than 30 keV) and the high (electrons greater than 200 keV and protons greater than 10 MeV) energy particles impinging on the telescope along its orbit.
The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is a proposed joint ESA/NASA/Russia gamma-ray astronomy mission which will provide both imaging and spectroscopy. It is currently at the final stages of an ESA phase-A study which it is hoped will lead to it being adopted during 1993 as the second 'medium-class' mission within ESA's Horizon 2000 plan. Launched in less than 10 years time it will be the successor to the current generation of gamma-ray spacecraft, NASA's Compton Observatory (GRO) and the Soviet- French Granat/Sigma mission. The baseline is to have two main instruments covering the photon energy range 50 keV to 10 MeV, one concentrating on high-resolution spectroscopy, the other emphasizing imaging. In addition there will be two monitors--an X-ray monitor which will extend the photon energy range continuously covered down to a few keV, and an Optical Transient Camera which will search for optical emission from gamma-ray bursts.
A novel low energy astronomical gamma-ray detector is being developed for future satellite missions. Recent advances in the technology of photodiodes and small, low noise amplifier circuits have meant that more compact detectors can be assembled in a complex array in order to give a 3-D position reconstruction capability. In a mask-detector telescope this capability is potentially very useful since it allows the reconstruction of the path of the incident gamma rays making it valuable both for imaging and background rejection. A small prototype of a 3-D detector has been realized for test in a balloon mission. The detector is based on a 12 X 8 array of position sensitive CsI(T1) bars, typically 15 cm long with 1.3 X 1.3 cm cross section, viewed at each end by photodiodes. The detector includes four 1.3 X 1.3 X 2.5 cm CsI(T1) scintillators located above the main array in order to evaluate the low energy response of the imager. The detector constitutes an active block of 2400 cm3 of scintillator that can operate in the 0.2 - 10 MeV energy range. The energy resolution is 13% at 662 keV and the positional resolution is of the order of 1.5 cm in each dimension. An active shield of CSI(T1) and plastic scintillators surrounds the bar detector. The overall experiment is briefly described in general and preliminary results of laboratory tests are presented.
The capabilities of the European Photon Imaging Camera (EPIC), the main instrument of ESA's 'Cornerstone' mission in X-ray astronomy with multiple mirrors (XMM), are discussed. The CCD characteristics, spatial resolution, energy bandpass and faint source sensitivity, spectral resolution and sensitivity, and timing capability are addressed, and the scientific rationale of the EPIC is summarized. The EPIC instrument system concept is briefly described.
Analytical considerations and test results bearing on the performance of a CsI(Tl) scintillating crystal coupled with a photodiode when used as a gamma-ray spectrometer are addressed. Laboratory test results on a number of CsI(Tl) bars with different sizes, diffusive coatings, and preamplifier designs are presented. A suitable event selection electronic logic design is shown which reduces the effect of noise on the count rate while retaining the desired energy threshold.