John H. Chappell

AXAF High-Resolution Camera (HRC): calibration and recalibration at XRCF and beyond

The high resolution camera (HRC) is a microchannel plate based imaging detector for the Advanced X-Ray Astrophysics Facility (AXAF) that will be placed in a high earth orbit scheduled for launch in August, 1998. An end-to-end calibration of the HRC and the AXAF high resolution mirror assembly (HRMA) was carried out at the Marshall Space Flight Centers X-Ray Calibration Facility (XRCF). This activity was followed by several modifications to the HRC to improve its performance, and a series of flat field calibrations. In this paper, and the following companion papers, we discuss the calibration plans, sequences, and results of these tests. At the time of this conference, the HRC has been fully flight qualified and is being integrated into the science instrument module (SIM) in preparation for integration into the AXAF spacecraft.

In-flight performance of the Chandra high-resolution camera

The High Resolution Camera (HRC) is one of the two focal plane instruments on NASAs Chandra X-ray Observatory which was successfully launched July 23, 1999. The Chandra Observatory will perform high resolution spectroscopy and imaging in the X-ray band of 0.1 to 10 keV. The HRC instrument consists of two detectors, the HRC-I for imaging and the HRC-S for spectroscopy. In this paper we present an overview of the in-flight performance of the High Resolution Camera and discuss some of the initial scientific results.

High-resolution camera (HRC) on the Advanced X-Ray Astrophysics Facility (AXAF)

The Advanced X-ray Astrophysics Facility (AXAF) is a major NASA space observatory and is scheduled for launch in 1998. AXAF will perform high spatial and spectral resolution observations of celestial sources in the soft x-ray band 0.1 - 10 keV. The high resolution camera (HRC) is one of two focal plane instruments being developed for the AXAF. The HRC will be capable of observing point and extended sources with high sensitivity and high spatial resolution and will be used to record the high resolution spectra produced by an objective transmission grating. The HRC is based on microchannel plates (MCPs). We describe the design and development of the HRC, its expected performance, and some of its observational goals. The HRC consists of two separate detectors, HRC-I (imaging) and HRC-S (spectroscopy). HRC-I is used for imaging and has a field of view of 31 arc min by 31 arc min and a spatial resolution of less than 25 micrometers (equivalent to less than 0.5 arc sec). HRC- S is optimized to readout the spectrum of AXAFs low energy transmission grating (LETG) and this combination will achieve resolving powers in excess of 1000 at low energies and cover a wavelength range of 4 to 140 angstroms.

Realistic inexpensive soft x-ray polarimeter and the potential scientific return

Using multilayer coated mirrors to provide high reflectivity at large graze angles, we have proposed to launch a small telescope that is capable of measuring the linear polarization of the soft x-ray fluxes from many astronomical sources. Three identical mirror-detectoer assemblies are designed for maximum efficiency at 0.25 keV, where the photon spectra of many celestial targets peak. In observations lasting 1-3 days using this low risk instrument with proven heritage, we can detect polarizations of 5-10% at 5σ due to Compton scattering or synchrotron processes in the relativistic jets of BL Lac objects, accretion disks or jets in active galactic nuclei and atmospheres of isolated pulsars. Pulsar data can be binned by pulse phase to measure the orientation of the neutron star rotation and magnetic field axes and constrain the mass to radius ratio. This project has been selected for technology development funding by the NASA Explorer Program.

In-flight Performance and Calibration of the Chandra High Resolution Camera Imager (HRC-I)

In this paper we present and compare flight results with the latest results of the ground calibration for the HRC-I detector. In particular we will compare ground and in flight data on detector background, effective area, quantum efficiency and point spread response function.

Performance and calibration of the AXAF High-Resolution Camera II: the spectroscopic detector

The high resolution camera (HRC) is one of two focal plane detector systems that will be flown on the Advanced X-ray Astrophysics Facility (AXAF). The HRC consists of two microchannel plate (MCP) detectors: one to provide large area, high position resolution imaging and timing (HRC-I), and a second (HRC-S) to provide a readout for the AXAF low energy transmission gratings. Each detector is composed of a chevron pair of CsI coated MCPs with a crossed grid charge detector and an Al/polyimide UV/ion shield. In this paper, we describe the operation, performance and calibration of the spectroscopic detector. In particular, we discuss the absolute quantum efficiency calibration, the point spread function of the instrument combined with the AXAF telescope, the count rate linearity, the spatial linearity, and the internal background of the instrument. Data taken in the laboratory and at the x-ray Calibration Facility at Marshall Space Flight Center are presented.

Improving Chandra High-Resolution Camera event positions via corrections to crossed-grid charge detector signals

The High Resolution Camera (HRC) on-board the Chandra X-ray Observatory (CXO) provides the highest resolution X-ray images of celestial sources ever taken. Unfortunately, ringing in the electronics compromises the position readout signals for some of the events. The compromised signals affect the angular resolution that can be achieved. We present an empirically derived algorithm that can be used in ground processing of the data to minimize the impact of the ringing on the calculated event positions.

In-flight performance and calibration of the Chandra high-resolution camera spectroscopic readout (HRC-S)

The High Resolution Camera (HRC) is one of two focal plane instruments on the NASA Chandra X-ray Observatory which was successfully launched on July 23, 1999. The Chandra X-ray Observatory was designed to perform high resolution spectroscopy and imaging in the X-ray band of 0.07 to 10 keV. The HRC instrument consists of two detectors, HRC-I for imaging and HRC-S for spectroscopy. Each HRC detector consists of a thin aluminized polyimide blocking filter, a chevron pair of microchannel plates and a crossed grid charge readout. The HRC-I is an approximately 100 X 100 mm detector optimized for high resolution imaging and timing, the HRC-S is an approximately 20 X 300 detector optimized to function as the readout for the Low Energy Transmission Grating. In this paper we discuss the in-flight performance of the HRC-S, and present preliminary analysis of flight calibration data and compare it with the results of the ground calibration and pre-flight predictions. In particular we will compare ground data and in-flight data on detector background, quantum efficiency, spatial resolution, pulse height resolution, and point spread response function.

Background reduction in microchannel plates

The source of an observed diffuse, time-varying structured background component in both bare and coated microchannel plates (MPCs) is investigated. The effects of MCP operating voltages, MCP gain characteristics, pressure, electrical contacts, and physical shielding on this background component are addressed. Various techniques to reduce this background are considered.

Performance and calibration of the AXAF High-Resolution Camera I: imaging readout

The high resolution camera (HRC) will be one of the two focal plane instruments on the Advanced X-ray Astrophysics Facility, (AXAF). AXAF will perform high resolution spectrometry and imaging in the X-ray band of 0.1 to 10 keV. The HRC instrument consists of two detectors, the HRC-I for imaging and the HRC-S for spectroscopy. Each HRC detector consists of a thin aluminized polyimide window, a chevron pair of microchannel plates (MCPs) and a crossed grid charge readout. The HRC-I is a 100 by 100 mm detector optimized for high resolution imaging and timing, the HRC-S is an approximately 30 by 300 mm detector optimized to function as the readout for the low energy transmission grating spectrometer (LETGS). In this paper we present the absolute quantum efficiency, spatial resolution, point spread response function and count rate linearity of the HRC-I detector. Data taken at the HRC laboratory and at the Marshall Space Flight Center X-ray Calibration Facility are presented. The development of the HRC is a collaborative effort between The Smithsonian Astrophysical Observatory, University of Leicester UK and the Osservatorio Astronomico, G.S. Vaiana, Palermo Italy.