UVISS is a square aperture Ritchey-Chretien telescope of 45x45 cm designed for accommodation on the International Space Station. The designed field corrector can give a corrected field of view larger than that required by the project; the optical surface of the corrector will be figured using the ion beam figuring technique, with an expected extremely good optics quality. UVISS will employ multilayer coatings for imaging in the near UV (130 - 260 nm) and possibly also far UV (90 - 115 nm) bands.
UVISS is a small telescope of 50 cm aperture designed for accommodation on the International Space Station, and it will employ multilayer coatings for imaging in the near UV (130 - 260 nm) and possibly also far UV (90 - 115 nm) bands. Near UV filters have been designed using MgF2, BaF2, Al2O3, SiO2, Y2O3, and the far UV filter has been designed using LiF and Y2O3. Tests are in progress on some of these coatings, including trade-off's between multilayers and Indium filters short-wards of Lyα. The first results are encouraging, since they show that the technique appears to be feasible.
In recent years massive CCD photometry has dramatically increased the number of known variable stars in the Milky Way and nearby galaxies of the Local Group. Some surveys are related to microlensing studies, distance determinations and the study of Cepheids and other pulsating stars, and are based on relatively small telescopes. The comparison of the performances of the various instruments shows the present limitations of the variable star research, and the requirements are to increase the sensitivity, spatial resolution and field of view. In order to get a better sensitivity, we adopted the Wh-photometry, or unfiltered observations. We discuss the merits and defects of this technique in the context of recent studies with the ESO 0.9m Dutch telescope and Wide Field Imager at the 2.2 m telescope. As regards the high precision photometry, we remark that a better control of the various error sources (including the stability of the instrumentation) is needed in order to detect very small amplitude variations with good confidence.
Pier Bernacca, Elio Antonello, F. Bertola, Andrea Martinez, Roberto Stalio, Santo Catalano, L. Maraschi, Marcello Rodono, Giuseppe Tondello, Gabriele Villa, M. Badiali, Giovanni Bonanno, Andrea Bucconi, L. Buson, D. Cardini, A. Cavaliere, P. Ceccherini, D. Martino, M. Della Valle, A. Emanuele, Renato Falomo, C. Facchinetti, E. Fantino, Anna Gregorio, Alessandro Lanzafame, C. Mirra, U. Munari, Giampiero Naletto, I. Pagano, Maria-Guglielmina Pelizzo, P. Pizzolati, Luca Poletto, Roberto Ragazzoni, R. Rampazzo, Bortolino Saggin, Salvatore Scuderi, Paolo Trampus, Michela Uslenghi, Mario Zannoni, Giovanna Zennaro, A. Bressan
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 optical/UV monitor (OM) on the ESA x-ray cornerstone mission XMM is designed to provide simultaneous optical and UV coverage of x-ray targets viewed by the observatory. The instrument consists of a 30 cm modified Ritchey-Chretien telescope. This feeds a compact photon counting detector operating in the blue part of the optical spectrum and the UV (1600 - 6000 angstrom). The OM has a square field of view of approximately 24 arcmin along the diagonal, and will cover the central region of the field of view of the EPIC x- ray cameras where the x-ray image quality is best. Because of the low sky background in space, the sensitivity of the OM for detecting stars will be comparable to that of a 4-m telescope at the Earth's surface; it should detect a B equals 24th magnitude star in a 1000 s observation using unfiltered light. The pixel size of the detector corresponds to 0.5 arc seconds on the sky in normal operation. In front of each of two redundant detectors are filter wheels containing broad band filters. The filter wheels also contain Grisms for low resolution spectroscopy of brighter sources (lambda/Delta lambda 200) and a 4x field expander which will allow high spatial resolution images of the field center to be taken in optical light.
The Optical Monitor is an ancillary instrument of the JET-X experiment on board of the satellite SPECTRUM-X-GAMMA. It consists of a Ritchey-Chretien telescope with an aperture of 230 mm, and two CCD detectors. The scientific objectives are the observations in the optical and UV band simultaneously with X-ray observations, the real time identification of X- ray sources with Mv <EQ 22 and detection of their variability, the improvement of the post-facto spacecraft attitude reconstruction (as a backup of the Attitude Monitor), and the serendipitous mode search for microvariability of the bright stars falling in the field of view.
The XMM Optical Monitor (XMM/OM) is a co-aligned telescope devoted to make observations of the X-ray sources both in the UV, visible and near-IR spectral bands, simultaneously with the X-ray instrument on the X-ray Multi-Mirror (XMM) satellite. The OM telescope is a Ritchey-Chretien with 300 mm clear aperture, for real time identification of sources up to magnitude mv equals 24. In the design of the telescope, particular care was paid in the selection of the optomechanical architecture and in the thermal and structural analysis, since the adopted optical scheme requires high stability of the structure. The paper highlights the major critical aspects and the criteria followed in the trade-off and design phases.
A multi-national consortium of research groups are developing the XMM (x-ray multi-mirror mission) optical monitor to provide a capability for optical identification and photometry of x-ray sources observed by the XMM observatory. This will be the first multi-wavelength facility dedicated to monitoring the variability of diverse sources from the optical through to x-ray wavelengths. Here we describe the system design and discuss progress in the breadboard phase of the development program.
The Optical/UV Monitor Telescope (XMM-OM) on the ESA X-ray Cornerstone mission XMM is designed to provide simultaneous optical and UV coverage of all sources viewed by the observatory in the X-ray band. The instrument consists of a 30 cm Ritchey-Chretien telescope. This feeds a compact photon counting detector that operates in the blue part of the optical spectrum and the UV (1600 - 5500 angstroms), and simultaneously a cooled CCD detector which registers the red light (5500 - 10000 angstroms). The XMM-OM will have a field of view of approximately 25 arcmin diameter, matching that of the X-ray cameras on XMM, and a spatial pixel size in normal operation of 1 arcsec in the blue, and about 1.8 arcsec in the red. Because of the low sky background in space, the sensitivity of the XMM- OM for detecting stars will be comparable to that of a 4-m telescope at the Earth's surface, and it should detect a B equals 24th magnitude star with a photon counting detector in a 1000 s observation using unfiltered light.
The Joint European X-ray Telescope, JET-X, is one of the core instruments in the scientific payload of the USSR''s Spectrum Roentgen-Gamma (RG) high energy astrophysics mission. JET-X consists of two identical co-aligned X-ray imaging telescopes, each with a spatial resolution of 20 arc second. Focal plane imaging is achieved with cooled X-ray sensitive CCD detectors, which provide high spectral resolution and good background rejection efficiency, in addition to the necessary imaging capability. An optical monitor telescope, also co-aligned with the two X-ray telescopes, permits simultaneous observation and identification of optical counterparts of X-ray target sources. The system design of JET-X is reviewed, and performance data obtained from measurements on the instrument prototype are presented.
The Optical Monitor is a part of the JET-X experiment which will fly on board the Soviet satellite Spectrum-X-Gamma. The reflector is a Ritchey-Chretien with an aperture of 260 mm, and there are two frame transfer CCD detectors. The scientific objectives of the Optical Monitor are observations in the optical and UV bands simultaneously with X-ray, the real time identification of X-ray sources with mv less than or equal to 22 and detection of their variability, the improvement of the post-facto spacecraft attitude reconstruction for the X-ray observations, and the serendipitous mode search for microvariability of the bright stars to develop the research field of asteroseismology. Since long integration times are required for the faint object detection, a dedicated servo loop operating on the secondary mirror is developed for the stabilization of the images against the drift of the satellite.
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