127,845 research outputs found
Active Thermal Control for the Multispectral Earth Sensors (ACMES) Mission
The Active Thermal Architecture (ATA) is a sub 1U active thermal control system providing payload thermal support and setpoint thermal control for the Active Cooling for Multispectral Earth Sensors (ACMES) mission. Based on a single-phase fluid loop heat exchanger, the ATA features a micro centrifugal pump, an innovative working fluid, and a two-axis flexible rotary fluid joint coupled to a deployable tracking radiator. The ATA system leverages advanced Ultrasonic Additive Manufacturing (UAM) techniques to directly integrate the ATA system within the payload and CubeSat structure. NASA\u27s Science Mission Directorate has selected the ATA system to fly on the ACMES mission. A 12U CubeSat technology demonstration funded by the In-space Validation of Earth Science Technologies (InVEST) program. The ATA will serve as payload support to the Hyperspectral Thermal Imaging instrument (HyTi). A high spectral/spatial density long-wave infrared (8-10.7 ÎŒm) instrument. HyTi also features advanced, onboard high-performance computing. The ATA will thermally support HyTi allowing for continuous operations. ACMES will also feature two student-led instrument development projects. A highly sensitive methane detector FINIS and a planar Langmuir/Impedance probe PLAID. ACMES will be a joint development effort between Orion Space, the University of Hawaii, and Utah State University
Advanced Synthetic Aperture Radar Based on Digital Beamforming and Waveform Diversity
This paper introduces innovative SAR system
concepts for the acquisition of high resolution radar images with
wide swath coverage from spaceborne platforms. The new concepts
rely on the combination of advanced multi-channel SAR front-end
architectures with novel operational modes. The architectures
differ regarding their implementation complexity and it is shown
that even a low number of channels is already well suited to
significantly improve the imaging performance and to overcome
fundamental limitations inherent to classical SAR systems. The
more advanced concepts employ a multidimensional encoding of
the transmitted waveforms to further improve the performance
and to enable a new class of hybrid SAR imaging modes that are
well suited to satisfy hitherto incompatible user requirements for
frequent monitoring and detailed mapping. Implementation
specific issues will be discussed and examples demonstrate the
potential of the new techniques for different remote sensing
applications
Range imager performance comparison in homodyne and heterodyne operating modes
Range imaging cameras measure depth simultaneously for every pixel in a given field of view. In most implementations the basic operating principles are the same. A scene is illuminated with an intensity modulated light source and the reflected signal is sampled using a gain-modulated imager. Previously we presented a unique heterodyne range imaging system that employed a bulky and power hungry image intensifier as the high speed gain-modulation mechanism. In this paper we present a new range imager using an internally modulated image sensor that is designed to operate in heterodyne mode, but can also operate in homodyne mode. We discuss homodyne and heterodyne range imaging, and the merits of the various types of hardware used to implement these systems. Following this we describe in detail the hardware and firmware components of our new ranger. We experimentally compare the two operating modes and demonstrate that heterodyne operation is less sensitive to some of the limitations suffered in homodyne mode, resulting in better linearity and ranging precision characteristics. We conclude by showing various qualitative examples that demonstrate the systemâs three-dimensional measurement performance
The Expanded Very Large Array
In almost 30 years of operation, the Very Large Array (VLA) has proved to be
a remarkably flexible and productive radio telescope. However, the basic
capabilities of the VLA have changed little since it was designed. A major
expansion utilizing modern technology is currently underway to improve the
capabilities of the VLA by at least an order of magnitude in both sensitivity
and in frequency coverage. The primary elements of the Expanded Very Large
Array (EVLA) project include new or upgraded receivers for continuous frequency
coverage from 1 to 50 GHz, new local oscillator, intermediate frequency, and
wide bandwidth data transmission systems to carry signals with 16 GHz total
bandwidth from each antenna, and a new digital correlator with the capability
to process this bandwidth with an unprecedented number of frequency channels
for an imaging array. Also included are a new monitor and control system and
new software that will provide telescope ease of use. Scheduled for completion
in 2012, the EVLA will provide the world research community with a flexible,
powerful, general-purpose telescope to address current and future astronomical
issues.Comment: Added journal reference: published in Proceedings of the IEEE,
Special Issue on Advances in Radio Astronomy, August 2009, vol. 97, No. 8,
1448-1462 Six figures, one tabl
Advances in infrared and imaging fibres for astronomical instrumentation
Optical fibres have already played a huge part in ground based astronomical
instrumentation, however, with the revolution in photonics currently taking
place new fibre technologies and integrated optical devices are likely to have
a profound impact on the way we manipulate light in the future. The
Anglo-Australian Observatory, along with partners at the Optical Fibre
Technology Centre of the University of Sydney, is investigating some of the
developing technologies as part of our Astrophotonics programme. In this paper
we discuss the advances that have been made with infrared transmitting fibre,
both conventional and microstructured, in particular those based on flouride
glasses. Flouride glasses have a particularly wide transparent region from the
UV through to around 7um, whereas silica fibres, commonly used in astronomy,
only transmit out to about 2um. We discuss the impact of advances in fibre
manufacture that have greatly improved the optical, chemical resistance and
physical properties of the flouride fibres. We also present some encouraging
initial test results for a modern imaging fibre bundle and imaging fibre taper.Comment: 11 pages, 7 figures, to be published in Proc. SPIE 6273
Optomechanical Technologies for Astronom
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