Search

UVSTAR, UltraViolet Spectrograph Telescope for Astronomical Research, operates in the 500–1250 A wave-band at 1 to 3 A resolution. Here we report on the EUV and FUV observations of the B2 II star Adara, the brightest EUV source in the sky, obtained by UVSTAR during the STS 69 and STS 95 missions. The discussion concerns 1) wavelength and flux calibration, 2) short term time variability of selected spectral features, 3) comparison with previous measurements in the EUV band and 4) comparison with model atmospheres.

A low-mass, low-cost photon-counting scientific payload has been developed and launched on a commercial microsatellite in order to study the near-UV night-sky background emission with a telescope nicknamed “Notte” and the Aurora emission with “Alba”. AURORA, this is the name of the experiment, will determine, with the “Notte” channel, the overall night-side photon background in the 300–400 nm spectral range, together with a particular 2 + N 2 line ( λ c =337 nm). The “Alba” channel, on the other hand, will study the Aurora emissions in four different spectral bands (FWHM=8.4–9.6 nm) centered on: 367 nm (continuum evaluation), 391 nm (1 − N + 2 ), 535 nm (continuum evaluation), 560 nm (OI). The instrument has been launched on the 26 September, 2000 from the Baikonur cosmodrome on a modified SS18 Dnepr-1 “Satan” rocket. The satellite orbit is nearly circular ( h apogee =648 km, e =0.0022), and the inclination of the orbital plane is 64.56°. An overview of the techniques adopted is given in this paper.

UVSTAR is an EUV spectral imager intended as a facility instrument devoted to solar system astronomy and to astronomy. It covers the wavelength range of 500 to 1250A, with sufficient spectral resolution to separate atomic emission lines and to form spectrally resolved images of extended plasma sources. Targets include the Io plasma torus at Jupiter, hot stars, planetary nebulae and extragalactic sources. UVSTAR will make useful measurements of emissions from the Earth's atmosphere as well. UVSTAR consists of a pair of telescopes and concave-grating spectrographs that cover the overlapping spectral ranges of 500–900Aand 850–1250A. The telescopes use two 30 cm diameter off-axis paraboloids having a focal length of 1.4 m. An image of the target is formed at the entrance slits of two concave grating spectrographs. The gratings provide dispersion and re-image the slits at the detectors, intensified CCDs. The readout format of the detectors can be chosen by computer, and three slit widths are selectable to adapt the instrument to specific tasks. The spectrograph package has internal gimbals which allow rotation of ±3° about each of two axes. Dedicated finding and tracking telescopes will acquire and track the target after rough pointing is achieved by orienting the Orbiter. Responsibilities for the implementation and utilization of UVSTAR are shared by groups the U.S. and Italy. UVSTAR is scheduled for flight in early 1994.

The characteristics of the fine pointing and tracking system of UVISS, UltraViolet Italian Space Surveyor, which is proposed to fly as an external payload attached to the ISS (International Space Station) Express Pallet is presented. The system is derived from the pointing system of the UVSTAR telescope that has flown three times on the Shuttle. The electro-optical architecture of the tracking telescope, including the ICCD detector and the computational unit based on a DSP board with direct high speed interface to the camera and the on-board stellar catalog is described. The simulations performed to determine the instrument expected tracking precision and performances considering the dynamics of the ISS are reported. Finally the utilization of a high frequency tracking error correction based on the detection of the spectrographs zero-th order signal is considered as an independent tracking error measurement which provides information and corrections of possible residual tracking errors and could be used for alignment check as well.

The characteristics of the fine pointing and tracking system of UVISS, UltraViolet Italian Space Surveyor, which is proposed to fly as an external payload attached to the ISS (International Space Station) Express Pallet is presented. The system is derived from the pointing system of the UVSTAR telescope that has flown three times on the Shuttle. The electro-optical architecture of the tracking telescope, including the ICCD detector and the computational unit based on a DSP board with direct high speed interface to the camera and the on-board stellar catalog is described. The simulations performed to determine the instrument expected tracking precision and performances considering the dynamics of the ISS are reported. Finally the utilization of a high frequency tracking error correction based on the detection of the spectrographs zero-th order signal is considered as an independent tracking error measurement which provides information and corrections of possible residual tracking errors and could be used for alignment check as well.

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.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We present the characteristics of a star mapper, AMICA, which could be used for determining the pointing direction of external payloads mounted on the International Space Station. AMICA, which is complementary to the GPS attitude determination system provided by the ISS, is a stand alone system able to provide both the pointing direction in the inertial reference frame with arc-sec precision at a 1 Hz rate and the angular orientation of the stellar field with slightly lower precision. The star mapper is derived from the pointing system of the UVSTAR telescope that has flown three times on the Shuttle. We present a description of the AMICA optical and electronics architecture and its functionality. We also give a summary of the key pointing/tracking results obtained during the Shuttle missions. Finally we report on simulations performed to determine the instrument expected precision and performances, including the percentage of recognized stellar fields. AMICA is presently considered for flying in support ...

The discovery of the extreme energy cosmic rays (EERC) with energy greater than 1020 eV has opened a new research branch of astrophysics on both observational and interpretative point of views. Together with the EECR one has also to consider the neutrino component which, independently on its primary or secondary origin, can reach comparable energies. These particles can be detected through the giant showers (EAS) produced in the Earth atmosphere and the induced fluorescent molecular nitrogen emission. Observing the EECR 'signals' is very difficult; we need forefront technology or new developments. The main reason is that their flux is very weak, typically of the order of a few events/year/1000 km2 per EECR of E approximately equals 1020 eV. The proposed Airwatch mission, base don a single orbiting telescope which can measure both intensity and direction of the EAS, impose new concepts for the detectors; single photon sensitivity, fast response of the order of few microseconds with sampling times of tenths of nanoseconds, low noise and good S/N ratio, large area, adaptability to a curved surface. Fortunately the spatial resolution requirements are somehow relaxed. The peculiar characteristics of this application are such that no available detectors satisfies completely the requirements. Therefore the final detector has to be the result of a R and D program dedicated to the specific problem. In this paper we survey a number of possible detectors and identify their characteristics versus the Airwatch mission requirements.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

UVSTAR, UV Spectrograph Telescope for Astronomical Research operates in the 500-1200 angstrom waveband; it has capability for long slit spectral imaging of extended cosmic sources. UVSTAR has recently flown as a Hitchhiker-M payload on the STS 85 mission of the SHuttle Discovery. UVSTAR is a joint collaboration between the University of Arizona and the University of Trieste. The instrument consists of a movable platform and an optical system The platform provides fine pointing within +/- 3 degrees from the nominal view direction, which is near the shuttle +Y axis, i.e. perpendicular to the long axis of the Shuttle and in the plane of the wings. The optical system has two channels, each formed of a telescope and Rowland concave-grating spectrograph with intensified CCD detector. The first channel, FUV, operates in the 850-1250 angstrom spectral range, the second, EUV, has covered the 500-900 angstrom region. UVSTAR includes capabilities for independent target acquisition and tracking. Here we report FUV observations, obtained in August 1997, of the sdO star BD +28 degrees 4211 which is a secondary flux standard and of the central star of the planetary nebula NGC 246, a hot degenerate star which shows strong OVI lines in the optical region. The UVSTAR spectrum of NGC 246 displays remarkable P Cygni profiles indicating a very fast stellar wind.

UVSTAR is an EUV spectral imager intended as a facility instrument devoted to solar system and astronomy studies. It covers the wavelength range of 500 to 1250 angstrom, with sufficient spectral resolution to separate emission lines and to form spectrally resolved images of extended plasma sources. Targets include the Io plasma torus at Jupiter, hot stars, planetary nebulae and bright galaxies. UVSTAR consists of a pair of telescopes and concave grating spectrographs that cover the overlapping spectral ranges of 500 - 900 and 850 - 1250 angstrom. The telescopes use two 30 cm diameter off-axis paraboloids having a focal length of 1.5 m. An image of the target is formed at the entrance slits of the two concave grating spectrographs. The gratings provide dispersion and re-image the slits at the detectors, intensified CCDs. The readout format of the detectors can be chosen by computer, and three slit widths are selectable to adapt the instrument to specific tasks. UVSTAR has internal gimbals which allow rotation of +/- 3 degree(s) about each of two axes. Dedicated finding and tracking telescopes will acquire and track the target after rough pointing is achieved by orienting the orbiter. Responsibilities for implementation and utilization of UVSTAR are shared by groups in Italy and the U.S. The first of the five approved UVSTAR flights is scheduled for May 1995.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

UVSTAR is an EUV spectral imager intended as a facility instrument devoted to solar system and astronomy studies. It covers the wavelength range of 500 to 1250 angstrom, with sufficient spectral resolution to separate emission lines and to form spectrally resolved images of extended plasma sources. Targets include the Io plasma torus at Jupiter, hot stars, planetary nebulae and bright galaxies. UVSTAR consists of a pair of telescopes and concave grating spectrographs that cover the overlapping spectral ranges of 500-900 and 850-1250 angstrom. The telescopes use two 30 cm diameter off-axis paraboloids having focal length of 1.5 m. An image of the target is formed at the entrance slits of the two concave grating spectrographs. The gratings provide dispersion and re-image the slits at the detectors, intensified CCDs. The readout format of the detectors can be chosen by computer, and three slit widths are selectable to adapt the instrument to specific tasks. UVSTAR has internal gimbals which allow rotation of +/- 3 degree(s) about each of two axes. Dedicated finding and tracking telescopes will acquire and track the target after rough pointing is achieved by orienting the Orbiter. Responsibilities for implementation and utilization of UVSTAR are shared by groups in Italy and the U.S. The first of the five approved UVSTAR flights is scheduled on May 1995.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Software for star field identification and star pointing and tracking is described. The software will be implemented in the guiding system of UVSTAR, a spectrograph/telescope system for UV astronomy and planetary physics that will operate as a Hitchhiker payload on the Shuttle. The software work with the wide-field CCD camera and an on-board stellar catalog. It is capable of (1) providing high accuracy (better than 2 arcsec) attitude determination from coarse (± 3 deg) initial knowledge of the pointing direction and (2) pointing toward the target. It is capable of tracking at the same high accuracy with a processing time of less than a few hundredths of a second. Simulation of observations and various types of tests are also discussed.

UVSTAR (Ultraviolet Spectrograph Telescope for Astronomical Research) is an EUV spectral imager intended as a facility instrument devoted to solar system and stellar astronomy. It covers the wavelength range of 500 to 1250 A, with sufficient spectral resolution to separate atomic emission lines and to form spectrally resolved images of extended plasma sources. Targets include the lo plasma torus at Jupiter, hot stars, and planetary nebulae. UVSTAR will make useful measurements of emissions from Earth's atmosphere as well. UVSTAR consists of a pair of telescopes and concave-grating spectrographs that cover the overlapping spectral ranges of 500 to 900 and 850 to 1250 A. The telescopes use two 30-cm-diam off-axis paraboloids having a focal length of 1.4 m. An image of the target is formed at the entrance slits of two concave grating spectrographs. The gratings provide dispersion and reimage the slits at the detectors, intensified CCDs. The readout format of the detectors can be chosen by computer, and three slit widths are selectable to adapt the instrument to specific tasks. The spectrograph package has internal gimbals, which allow rotation of ±3 deg about each of two axes. Dedicated finding and tracking telescopes will acquire and track the target after rough pointing is achieved by orienting the Orbiter. Responsibilities for the implementation and utilization of UVSTAR are shared by groups in Italy and the United States. UVSTAR is scheduled for flight in early 1995, timed for an opportunity to observe the Jovian system.