High Energy Astrophysics (HEA) encompasses a broad range of astrophysical science, with sources that include stars and stellar clusters, compact objects (black holes, neutron stars, and white dwarfs), supernova remnants, the interstellar medium, galaxies and clusters of galaxies, Active Galactic Nuclei (AGN), and gamma ray bursters, as well as a variety of fundamental physical processes. The physics involved includes extremes of gravity, density and magnetic field and is often inaccessible via any other waveband. HEA investigates and answers crucial questions in all fields of contemporary astrophysics.
Unlike the focusing of radio and optical light, X-rays are brought to focus through shallow, grazing incident angles. The analogy of skimming a stone across a pond is appropriate in describing how X-rays are focused. The higher the energy of the X-ray photon the shallower the incident angle must be, thereby introducing the requirement of longer focal lengths for focusing high-energy X-rays (E > 10 keV). This technical challenge has hindered scientific advancement in the high-energy regime, while at lower X-ray energies the community has prospered immensely with spectacular data from focusing observatories like XMM-Newton, Chandra, and Suzaku. Now, with ASTRO-H, the community will reap similar rewards from the tremendous improvement in spatial and spectral resolution at high energies. ASTRO-H is a JAXA mission. More information can be found on the ASTRO-H web site .
Because of the grazing-angle optics, high-energy X-ray instruments have a long focal length. The Hard X-ray Imager (HXI) of ASTRO-H has its detector housed in a boom that will extend by about 6 m in orbit so that a focal length of 12 m can be achieved for that instrument. This long structure will inevitably oscillate and flex, especially when passing across the orbital day/night boundary. In order to retain the essential imaging resolution, it is important that the boom has a metrology system that measures this flexion in order to allow post-acquisition compensation in generating the science images. In the current paper, we describe a possible Alignment Monitoring System (AMS) to measure in real time the relative position of the boom. The AMS will be an important element to guaranty that the ASTRO-H observatory will meet its performance requirements.
The Canadian Space Agency has the intention of providing the AMS to the ASTRO-H mission. The current paper reports a study that was conducted to support that intention.
The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) is the main instrument on-board the SCISAT-1 satellite, a mission mainly supported by the Canadian Space Agency . It is in Low- Earth Orbit at an altitude of 650 km with an inclination of 74E. Its data has been used to track the vertical profile of more than 30 atmospheric species in the high troposphere and in the stratosphere with the main goal of providing crucial information for the comprehension of chemical and physical processes controlling the ozone life cycle. These atmospheric species are detected using high-resolution (0.02 cm-1) spectra in the 750-4400 cm-1 spectral region. This leads to more than 170 000 spectral channels being acquired in the IR every two seconds. It also measures aerosols and clouds to reduce the uncertainty in their effects on the global energy balance. It is currently the only instrument providing such in-orbit high resolution measurements of the atmospheric chemistry and is often used by international scientists as a unique data set for climate understanding.
The satellite is in operation since 2003, exceeding its initially planned lifetime of 2 years by more than a factor of 5. Given its success, its usefulness and the uniqueness of the data it provides, the Canadian Space Agency has founded the development of technologies enabling the second generation of ACE-FTS instruments through the High Vertical Resolution Measurement (HVRM) project but is still waiting for the funding for a mission.
This project addresses three major improvements over the ACE-FTS. The first one aims at improving the vertical instantaneous field-of-view (iFoV) from 4.0 km to 1.5 km without affecting the SNR and temporal precision. The second aims at providing precise knowledge on the tangent height of the limb observation from an external method instead of that used in SCISAT-1 where the altitude is typically inferred from the monotonic CO2 concentration seen in the spectra. The last item pertains to reaching lower altitude down to 5 km for the retrieved gas species, an altitude at which the spectra are very crowded in terms of absorption. These objectives are attained through a series of modification in the optical train such as the inclusion of a field converter and a series of dedicated real-time and post-acquisition algorithms processing the Sun images as it hides behind the Earth. This paper presents the concepts, the prototypes that were made, their tests and the results obtained in this Technology Readiness Level (TRL) improvement project.
CARVE-FTS is a near-IR Fourier-Transform Spectrometer (FTS) used by the Jet Propulsion Laboratory (JPL) for the
Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE). CARVE is a 5-year mission of intensive aircraft
campaigns in the Alaskan Arctic selected as part of NASA’s Earth Ventures program (EV-1). The CARVE-FTS has
been designed, manufactured and tested by ABB Inc. The objective of this instrument is to provide integrated column
measurements of carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO). The system is inspired from the TSUKUBA-FTS built by ABB for the Japanese Aerospace Exploration Agency (JAXA). JAXA uses the instrument for preparation, calibration and validation within the GOSAT program. The instrument is a Michelson based FTS with three spectral bands. The light modulator is a Michelson single pass type interferometer with large aperture and medium spectral resolution. It provides infrared spectra from 12,900 cm-1 to 13,200 cm-1, from 5,800 cm-1 to 6,400 cm-1, and from 4,200 cm-1 to 4,900 cm-1. This instrument is also able to measure
the scene radiance with S and P polarization simultaneously using monopixel detectors. The instrument is mounted on a
damping platform and is installed in an aircraft. It delivers continuous data for flight campaigns over the Alaskan Arctic.
SNR higher than 100 is reached for each band and the measured ILS full width at half maximum is as low as 0.26 cm-1 at
6,566 cm-1. We present the instrument design, its specification and test results obtained at ABB.
THz imaging is a very promising field rapidly growing in importance. This expanding field is at its early stage of
development but already a large number of applications are foreseen. THz imaging promises to be a key technology in
various fields, such as defense & security where it can be used to defeat camouflage. Based on its many years of
experience in uncooled bolometers technology, INO has developed, assembled and characterized a prototype THz
imager. The camera's 160 × 120 pixel array consists of pixels with a 52 μm pitch that have been optimized for the THz
region. Custom camera electronics and an F/1 THz lens barrel complete the imager design. Real-time imaging at video
rate of 30 frame/sec has been performed with a 3 THz quantum cascade laser set-up. THz images of numerous object-obscurant
combinations are presented, proving the feasibility of video imaging in security screening applications.
We have previously reported on the initial development of a multi-linear uncooled microbolometer FPA for
space applications. The IRL512 FPA features three parallel lines of 512 pixels on a 39 micron pixel pitch
with parallel integration of all pixels, a complete detector bridge per pixel for offset and substrate
temperature drift compensation, and one 14-bit digital output bus per line. The FPA achieves an NETD
below 45 mK over the LWIR spectral band with 50 ms integration time, 300 K scene temperature, and
f/0.87 optics. In the context of the NIRST instrument for the upcoming SAC-D/Aquarius earth observation
mission, MWIR and LWIR optimized versions of the IRL512 in radiometric packages including integrated
stripe filter and radiation shield have recently successfully undergone screening and qualification
campaigns. The qualification strategy consists of part element and device qualification including proton
and total dose radiation, shock, vibration, burn-in, and thermal cycling. The test conditions and results will
be reviewed. The thermal resolution of the current generation of radiometrically packaged IRL512 FPA in
the NIRST instrument is below 500 mK with an 0.9 micron spectral bandwidth centred at 10.85 μm, 50 ms
integration time, the NIRST f/1 optics, and 300 K scene temperature.
A prototype THz imaging system based on modified uncooled microbolometer detector arrays, INO MIMICII camera
electronics, and a custom f/1 THz optics has been assembled. A variety of new detector layouts and architectures have
been designed; the detector THz absorption was optimized via several methods including integration of thin film metallic
absorbers, thick film gold black absorbers, and antenna structures. The custom f/1 THz optics is based on high resistivity
floatzone silicon with parylene anti-reflection coating matched to the wavelength region of interest. The integrated
detector, camera electronics, and optics are combined with a 3 THz quantum cascade laser for initial testing and
evaluation. Future work will include the integration of fully optimized detectors and packaging and the evaluation of the
achievable NEP with an eye to future applications such as industrial inspection and stand-off detection.
INO has established a VOx-based uncooled microbolometer detector technology and an expertise in the development of
custom detectors and focal plane arrays. Thanks to their low power consumption and broadband sensitivity, uncooled
microbolometer detectors are finding an increased number of applications in the field of space-based thermal remote
sensing. A mission requirement study has identified at least seven applications with a need for data in the MWIR (3-8
μm), LWIR (8-15 μm) and or FIR (15-100 μm) wavelength bands. The requirement study points to the need for two
main classes of uncooled thermal detectors, the first requiring small and fast detectors for MWIR and LWIR imaging
with small ground sampling distance, and the second requiring larger detectors with sensitivity out to the FIR. In this
paper, the simulation, design, microfabrication and radiometric testing of detectors for these two classes of requirements
will be presented. The performance of the experimental detectors closely approach the mission requirements and show
the potential of microbolometer technology to fulfill the requirements of future space based thermal imaging missions.