The Origins Space Telescope (OST) will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did the universe evolve in response to its changing ingredients? How common are life-bearing planets? To accomplish its scientific objectives, OST will operate at mid- and far-infrared wavelengths and offer superlative sensitivity and new spectroscopic capabilities. The OST study team will present a scientifically compelling, executable mission concept to the 2020 Decadal Survey in Astrophysics. To understand the concept solution space, our team studied two alternative mission concepts. We report on the study approach and describe both of these concepts, give the rationale for major design decisions, and briefly describe the mission-enabling technology.
A light weight, low power instrument called Multi Wavelength Dielectrometer
(MWD) to measure subsurface properties of planetary surfaces is described. The MWD
instrument consists of essential electronics and metallic plates acting as electrodes
attached to the body of space crafts. An electric signal applied to one of the electrodes
acting as a cathode sets up electric field pattern (in the soil medium) between the cathode
and other electrodes acting as anodes. The electrodes are swept through multiple
wavelengths (1Hz-MHz) and the electric current drawn by the electrodes or mutual
capacitances between electrodes is measured at each frequency. The measured
capacitances whose values depend upon electrode spacing, dielectric constant of the
subsurface soil, and the frequency are then used to estimate electrical properties of the
The NASA RADSTAR instrument is a compact scatterometer-radiometer system designed for airborne and space
remote sensing of Earth surface properties such as soil moisture and sea surface salinity. In this paper we describe the
active portion of RADSTAR, the L-band Imaging Scatterometer (LIS). The system employs electronic steering and
digital beamforming techniques to generate multiple, low-sidelobe beams over a scan range of +/-50 degrees below an
aircraft. We discuss the design and testing of LIS, and the planned merging of the scatterometer with the radiometric
components of the final instrument. In its final configuration, RadSTAR will employ a single broadband antenna to
efficiently support simultaneous scatterometer (LIS) and radiometer measurements in airborne and spaceborne
applications. LIS is currently being flown along with the ESTAR synthetic aperture radiometer aboard the NASA P-3
aircraft in order to prove the concept of coregistered data, setting the path for future spaceborne, single aperture,
electronically scanned, radar/radiometer systems.
This paper discusses the concept and design of a real-time Digital Beamforming Synthetic Aperture Radar (DBSAR) for
airborne applications which can achieve fine spatial resolutions and wide swaths. The development of the DBSAR
enhances important scientific measurements in Earth science, and serves as a prove-of-concept for planetary exploration
missions. A unique aspect of DBSAR is that it achieves fine resolutions over large swaths by synthesizing multiple
cross-track beams simultaneously using digital beamforming techniques. Each beam is processed using SAR algorithms
to obtain the fine ground resolution without compromising fine range and azimuth resolutions. The processor uses an
FPGA-based architecture to implement digital in-phase and quadrature (I/Q) demodulation, beamforming, and range
and azimuth compression. The DBSAR concept will be implemented using the airborne L-Band Imaging Scatterometer
(LIS) on board the NASA P3 aircraft. The system will achieve ground resolutions of less than 30 m and swaths of 10
km from an altitude of 8 km.
Improving the understanding of the Cryosphere and its impact on global hydrology is an important element of NASA’s Earth Science Enterprise (ESE). A Cold Land Processes Working Group (CLPWG) was formed by the NASA Terrestrial Hydrology Program to identify important science objectives necessary to address ESE priorities. These measurement objectives included Snow Water Equivalent (SWE), snow wetness, and freeze/thaw status of underlying soil. The spatial resolution requirement identified by the CLPWG was 100 m to 5000 m. Microwave sensors are well suited to measure these and other properties of interests to the study of the terrestrial cryosphere. It is well known that the EM properties of snow and soil at microwave frequencies are a strong function of the phase of water, i.e. ice/water. Further, both active and passive microwave sensors have demonstrated sensitivity to important properties of snowpack including, depth, density, wetness, crystal size, ice crust layer structure, and surface roughness. These sensors are also sensitive to the underlying soil state (frozen or thawed). Multiple microwave measurements including both active and passive sensors will likely be required to invert the effects of various snowpack characteristics, vegetation, and underlying soil properties to provide the desired characterization of the surface and meet the science needs required by the ESE. A major technology driver with respect to fully meeting these measurement needs is the 100 to 5000 m spatial resolution requirement. Meeting the threshold requirement of 5000 m at microwave frequencies from Low Earth Orbit is a technology challenge. The emerging capabilities of unmanned aircraft and particularly the system perspective of the Autonomous Aerial Observation Systems (AAOS) may provide high-fidelity/high-resolution measurements on regional scales or larger that could greatly improve our measurement capability. This paper explores a vehicle/sensor concept that could augment satellite measurements to enhance our understanding of the Cryosphere. The measurement performance and technology issues related to the sensor and aircraft will be assessed. Finally, specific technology needs and research necessary to enable this AAOS concept will be discussed.