The HEAO-A Scanning Modulation Collimator Instrument

Roy, Adrian G.; Ballas, J.; Jagoda, N.; McKlnnon, Phillip; Ramsey, A.; Wester, E.

doi:10.1109/tns.1977.4328786

Cited by 4 publications

(3 citation statements)

References 1 publication

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“…For collimator type X-ray telescopes, the in-flight calibration of alignment and PSF is accomplished by scanning the bright, identified sources with accurate positions [6], such as the Crab Nebula (hereafter the Crab). The principal of the calibration is as follows: Assuming that there is no misalignment between the collimators and the star tracker, then the observed position of the Crab can be inferred, and the offset between the inferred position and the real position corresponds to the misalignment, while the distribution of the counts represents the shape of the PSF.…”

Section: Calibration Scenariosmentioning

confidence: 99%

“…Consequently, the accurate in-flight calibration of the collimator alignment and PSF is strongly required. Actually, alignment and PSF calibrations have been executed for almost all X-ray and gamma-ray telescopes, including collimator type telescopes, such as HEAO-1 [6], HEXTE (private communication), and non-collimator type telescopes, like HETE-2 [7], Suzaku [8] and Fermi [9].…”

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confidence: 99%

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Simulation of the in-flight calibration of the collimator alignment and PSF for HXMT

Xiong

2010

Sci. China Phys. Mech. Astron.

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The Hard X-ray Modulation Telescope (HXMT) is an X-ray astronomical satellite in 1-250 keV, consisting of three collimated instruments. We present the in-flight calibration approach of the collimator alignment and Point Spread Function (PSF) for HXMT, using both the direct fitting method and the imaging method. According to observational simulations of the Crab Nebula, we find that these two methods produce almost the same calibration accuracy of the alignment, and with a one-day scanning observation, the alignment can be calibrated to better than 0.45′ and 0.1′ along the wide and narrow directions of the Field of View (FOV) for a detector module, which corresponds to a localization accuracy of better than 0.1′ and meets the scientific requirement. HXMT, alignment, PSF, calibrationThe Hard X-ray Modulation Telescope (HXMT) [1, 2] is an X-ray satellite working in 1-250 keV, consisting of three collimated instruments: the High Energy X-ray telescope (HE, 20-250 keV), the Medium Energy X-ray telescope (ME, 5-30 keV) and the Low Energy X-ray telescope (LE, 1-15 keV). HXMT will perform an all-sky scan survey with the highest sensitivity and angular resolution in 20-250 keV by using the Direct Demodulation (DD) image reconstruction method [3,4]. It will also carry out pointing observations to investigate the temporal and spectral properties of compact objects such as black hole and neutron star binaries.For a collimator type X-ray telescope, the boresight and PSF of the collimator need to be accurately calibrated to eliminate the systematic errors and to obtain reliable scientific results. For HXMT, the boresights of all the collimators of HE, ME and LE are designed to be parallel to that of the star tracker (see Figure 1). In order to decompose the background from the observation data and to improve the sensitivity, the combined Field of View (FOV) method and the off-axis method [5] are employed, demanding that each of the HE, ME and LE is configured with several kinds of FOVs (i.e. PSFs).However, small deviations in both boresight and PSF are expected due to the fabrication uncertainty, launch vibrations as well as relaxation in zero gravity in orbit. The deviations of boresight and PSF will contribute errors to the source localization, background calculation, spacecraft attitude control, flux estimation of the observed sources and so on. Consequently, the accurate in-flight calibration of the collimator alignment and PSF is strongly required. Actually, alignment and PSF calibrations have been executed for almost all X-ray and gamma-ray telescopes, including collimator type telescopes, such as HEAO-1 [6], HEXTE (private communication), and non-collimator type telescopes, like HETE-2 [7], Suzaku [8] and Fermi [9].

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Section: Calibration Scenariosmentioning

confidence: 99%

mentioning

confidence: 99%

Simulation of the in-flight calibration of the collimator alignment and PSF for HXMT

Xiong

2010

Sci. China Phys. Mech. Astron.

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“…Consequently, an in-orbit PSF calibration is essential to obtain accurate and reliable results from the scanning observations of Insight-HXMT. Almost all X-ray and gamma-ray telescopes performed the alignment and PSF calibrations after launch, such as HEAO-1 (Roy et al, 1977), Fermi (Ackermann, 2012), Nustar (Madsen et al, 2015) and MAXI (Hiroi et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

In-orbit calibration to the point-spread function of Insight-HXMT

Nang

Liao

Sai

et al. 2020

Journal of High Energy Astrophysics

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We make the in-orbit calibration to the point-spread functions (PSFs) of the collimators of the Hard X-ray Modulation Telescope with the scanning observation of the Crab. We construct the empirical adjustments to the theoretically calculated geometrical PSFs. The adjustments contain two parts: a rotating matrix to adjust the directional deviation of the collimators and a paraboloidal function to correct the inhomogeneity of the real PSFs. The parameters of the adjusting matrices and paraboloidal functions are determined by fitting the scanning data with lower scanning speed and smaller intervals during the calibration observations. After the PSF calibration, the systematic errors in source localization in the Galactic plane scanning survey are 0 • .010, 0 • .015, 0 • .113 for the Low-Energy Telescope (LE), the Medium-Energy telescope (ME) and the High-Energy telescope (HE), respectively; meanwhile, the systematic errors in source flux estimation are 1.8%, 1.6%, 2.7% for LE, ME and HE, respectively.

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Modulation patterns of astronomical imaging systems based on rotating grids

Dadurkevičius

Ralys

1985

Astrophys Space Sci

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The HEAO-A Scanning Modulation Collimator Instrument

Cited by 4 publications

References 1 publication

Simulation of the in-flight calibration of the collimator alignment and PSF for HXMT

Simulation of the in-flight calibration of the collimator alignment and PSF for HXMT

In-orbit calibration to the point-spread function of Insight-HXMT

Modulation patterns of astronomical imaging systems based on rotating grids

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