Balloon-borne Gamma-ray Telescope Research Articles

Development of the imaging system of the balloon-borne gamma-ray telescope Máscara Codificada (MASCO)

We report laboratory imaging results of a balloon-borne gamma-ray imaging telescope, Máscara Codificada (Portuguese for “coded mask,”) designed to obtain high angular resolution (∼14 arcmin) images of the sky in the 50 keV–1.8 MeV energy range. The instrument incorporates a coded mask with an aperture pattern based on a 19×19-element modified uniformly redundant array (MURA). This pattern belongs to a subclass of MURAs that are almost completely antisymmetrical for 90° rotations with respect to the lower-right corner of the central element, which allows the implementation of an antimask by a single rotation of the whole mask by 90°. The symmetry properties of the MURAs are discussed. The algorithm for determining the position of the gamma-ray interactions on the instrument’s main detector is described and the results of laboratory tests of the imaging system are presented. The mask–antimask subtraction, applied after a flat-fielding procedure, produced a 60% increase in the signal-to-noise ratio of a strong (∼100σ) point source (662 keV photons coming from a Cs137 radioactive source) image by eliminating systematic distortions in the instrumental background measured over the detector plane.

Development of an attitude control system for a balloon-borne gamma ray telescope

Abstract We describe the attitude control system employed by the MASCO balloon-borne gamma ray telescope and present the first laboratory tests of this system. The MASCO experiment is a low energy gamma ray imaging telescope that employs a MURA coded mask. Its angular resolution is 14′ over a 13° field of view, which requires a pointing accuracy of some arcminutes in order to allow the accomplishment of the scientific goals. The attitude control system was designed to provide pointing and stabilization of a 1400 kg, 7 m-high, 2 m-wide, 2 m-deep gondola that encompasses the telescope detector system and its associated electronics. The sensors used are an electronic magnetic compass, an encoder, a two-axis solar sensor, a sun-tracker, two accelerometers, a gyroscope and three CCD stellar sensors. A GPS system is also employed. The actuators are a reaction wheel for azimuth control, an azimuth motor located in the balloon-gondola decoupling mechanism for desaturation of the reaction wheel, and a telescope elevation motor with a harmonic drive reduction. The software architecture and the operation modes are also presented.

The in-flight performance of the ZEBRA day-time star sensor

The low energy balloon-borne gamma-ray telescope ZEBRA is capable of producing images of the sky with a resolution of 1° and a point source location accuracy of a few arcminutes. In order to fully exploit the sensitivity of this instrument, a platform stabilised in three axes to this precision has been developed, which however has an absolute pointing accuracy of 30′-1°. Therefore there is a need to have on board a system which will allow post facto reconstruction of the absolute pointing direction of the telescope as a function of time, for observations in both day- and night-time conditions. An independently steerable starsensor has been constructed, based on a CCD imaging system, for this purpose. The results obtained with this device during the first flight of the ZEBRA telescope in May 1989 from the NASA balloon base in Palestine, Texas are presented.

Detection of a weak gamma-ray burst from the direction of Ursa Major

An 80-second gamma-ray burst was detected over the energy range 42-205 keV by a balloon-borne gamma-ray telescope at 23:00:22 UT on May 11, 1988. Assuming a uniformly distributed source model, a 30 keV energy threshold, and a 3 delta detection threshold, it is estimated that the burst rate is 39,000 + 90,000 - 32,000/yr. It is found that the emission originated from the direction of Ursa Major. The event displays a marginal periodicity with a fundamental period 2.17 + or - 0.12 s.

Observations of Nuclear Reactors on Satellites with a Balloon-Borne Gamma-Ray Telescope

Gamma rays at energies of 0.3 to 8 megaelectron volts (MeV) were detected on 15 April 1988 from four nuclear-powered satellites including Cosmos 1900 and Cosmos 1932 as they flew over a double Compton gamma-ray telescope. The observations occurred as the telescope, flown from a balloon at an altitude of 35 kilometers from Alice Springs, Australia, searched for celestial gamma-ray sources. The four transient signals were detected in 30 hours of data. Their time profiles show maxima with durations of (21 +/- 1) and (27 +/- 1) seconds (half-width at half maximum) for the lower two satellites and (85 +/- 5) and (113 +/- 7) seconds for the remaining two. Their durations place the origin of the two shorter signals at orbital radii of 260(+40)(-60) and 260 +/- 60 km above the earth and the two longer at 800(+100)(-300) and 800(+250)(-300) kilometers. Their luminosities for energies >0.3 MeV are then (6.1 +/- 1.5) x 10(15), (3.9 +/- 1.0) x 10(15), (1.10 +/- 0.28) x 10(16), and (1.30 +/- 0.32) x 10(16) photons per second. The imaging of the strongest signal indicates a southeastern direction passing nearly overhead. The energy spectrum can be fit to an exponential with index 2.4 +/- 1.4. These transient events add to the already large backgrounds for celestial gamma ray sources.

The observation of the galactic anticenter region by the balloon borne gamma-ray telescope Natalya-I

This paper presents the results of measurements of gamma radiation with energies above 5 MeV, from the galactic anticenter region. The balloon-borne gamma ray telescope “Natalya-I”, was launched on 6 November, 1980 from the Tata Institute of Fundamental Research's Balloon Facility (Hyderabad, India) and reached ceiling altitude of 35 km. The results on the accelerator calibration of the telescope, using a “tagged” gamma ray beam are also presented.

Observation of Cygnus X-1 in the energy range 100 keV-3 MeV

view Abstract Citations (23) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of Cygnus X-1 in the energy range 100 keV - 3 MeV. Mandrou, P. ; Niel, M. ; Vedrenne, G. ; Dupont, A. ; Hurley, K. Abstract Cyg X-1 was observed 1976 June 5-6, in the energy range 100 keV-3 MeV by means of an 80 sq cm balloon-borne gamma-ray telescope, while the source was in the 'low' state. The energy spectrum is given and compared with previous results at lower and higher energies. Publication: The Astrophysical Journal Pub Date: January 1978 DOI: 10.1086/155775 Bibcode: 1978ApJ...219..288M Keywords: Balloon Sounding; Binary Stars; Gamma Ray Astronomy; X Ray Astronomy; X Ray Stars; Balloon-Borne Instruments; Data Reduction; Energy Spectra; Gamma Ray Telescopes; Photoelectron Spectroscopy; Astronomy; Energy Spectra:X-Ray Sources full text sources ADS | data products SIMBAD (2)

Observations with a high-resolution balloon-borne gamma-ray telescope

view Abstract Citations (13) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations with a high-resolution balloon-borne gamma-ray telescope. McKechnie, S. P. ; Mount, K. E. ; Ramsden, D. Abstract A balloon-borne spark-chamber telescope, having a threshold energy of 70 MeV and a projected full angular error of 1.2 deg at 300 MeV, was flown on three occasions between October 1972 and July 1973. Results from these flights, including observations of the Cygnus region, the Crab Nebula, and part of Hercules, are presented. An excess flux was observed from the galactic plane in the region of Cygnus, giving a line flux of about 0.000047 photon/sq cm/s/r. Positive fluxes were observed from the Crab Nebula and Cygnus X-4. Upper limits are quoted for other possible sources in the Cygnus region. Publication: The Astrophysical Journal Pub Date: August 1976 DOI: 10.1086/182201 Bibcode: 1976ApJ...207L.151M Keywords: Balloon-Borne Instruments; Crab Nebula; Gamma Rays; Spaceborne Telescopes; X Ray Sources; Astronomical Coordinates; High Resolution; Milky Way Galaxy; Spark Chambers; Astronomy full text sources ADS | data products SIMBAD (7)