The advent of small satellites and miniaturized instrument technology enables a new paradigm for observation from Low Earth Orbit (LEO). Passive microwave radiometer systems, such as SSM/I, AMSR-E, AMSU, ATMS, WindSat and GMI, have been providing important Earth observations for over 30 years, including but not limited to surface wind vector, atmospheric and surface temperature, water vapor, clouds, precipitation, snow and sea ice. Over the past several years, there has been a push to develop small satellite solutions for these critical measurements. The lower deployment cost of small satellites allows us to consider new ways to use these systems for Earth observation. Specifically, we may consider homogenous or heterogeneous constellations with the sensor elements either distributed in several orbit planes to improve revisit time, or as closely spaced trains to resolved short time scale processes, such as developing convection.
In this presentation, we will discuss three recently developed, complementary small satellite technology demonstration sensors that span the capability currently offered by the existing fleet of microwave environmental sensors. These systems are COWVR, a low-frequency fully-polarimetric conical imager, TEMPEST-D, a mm-wave cross-track imager/sounder and TWICE, a conical sub-mm wave imager/sounder. COWVR is a technology demonstration sensor for the US Air Force designed to be a small-satellite equivalent to sensors such as SSM/I, AMSR, WindSat and GMI. TEMPEST-D is a NASA Earth Ventures technology demonstration project and has equivalence with cross-track sounders such as AMSU, ATMS and MHS. TWICE, built under a NASA technology project, covers frequencies band not yet flown in space. Combined, these systems offer the potential to image the Earth from 6-800 GHz. When deployed in a constellation, they enable new observations of dynamic physical processes and coupling between land, ocean, atmosphere and cryosphere.
In this presentation, we will highlight the sensor design and status of each of the three radiometer technology demonstration projects. TEMPEST-D has been continuously operating on-orbit since September 2018 and COWVR is due to launch no earlier than January 2021. We will describe unique observations enabled by these systems when used in constellations, including time resolved measurements of dynamic atmospheric processes (e.g. developing convection) simultaneously with surface and atmospheric fluxes. We will show measured performance comparisons between these new small-sat sensors to the equivalent operational sensor, giving examples of on-orbit comparisons for TEMPEST-D and pre-launch measured data from COWVR and TWICE. Finally, we will discuss new mission concepts enabled by constellation sensor trains and distributed constellations, particularly as it relates to the observation goals identified in the US NRC Decadal Survey. We will highlight the potential for multi-sensor small-satellite constellations, showing recently acquired passive microwave and precipitation radar data from TEMPEST-D and RainCube.
Earth’s ionosphere responds dynamically over a wide range of temporal and spatial scales to changes in the magnetosphere and solar wind from above, and to neutral atmospheric dynamics from below. Determining the dynamics and coupling of Earth's magnetosphere, ionosphere, and atmosphere by vector magnetic field measurements at all altitudes is essential, as the field plays a major role in controlling the distribution of ionospheric plasma. It is difficult to measure the magnetic B-field, either locally or globally, at the altitudes of the upper mesosphere and lower thermosphere (UMLT) where the transfer of energy and momentum between the plasma and neutral components of the system occur. The 118-GHz imaging magnetometer will measure all four Stokes parameters as a function of frequency about the Zeeman-split center of the 118-GHz molecular oxygen line. We are developing an array of fully-polarimetric millimeterwave radiometer/spectrometers operating near 118 GHz. These low cost, low power, low mass polarimetric 118 GHz millimeter-wave array receivers do not require cooling to meet the sensitivity requirements. With digital spectrometers we will be able to integrate the complete end-to-end system. This work will enable a second generation small satellite mission with an off-nadir viewing instrument comprised of 120 such receivers (arranged so that each spot on the Earth is observed simultaneously by four receivers each) that will globally map the magnetic field in the mesosphere at 42-76 km altitude at a horizontal resolution ~100 km with 1-sigma error of 40-120 nT, in typical mesospheric temperature conditions.
In this paper we discuss the latest developments of the STRIP instrument of the “Large Scale Polarization Explorer” (LSPE) experiment. LSPE is a novel project that combines ground-based (STRIP) and balloon-borne (SWIPE) polarization measurements of the microwave sky on large angular scales to attempt a detection of the “B-modes” of the Cosmic Microwave Background polarization. STRIP will observe approximately 25% of the Northern sky from the “Observatorio del Teide” in Tenerife, using an array of forty-nine coherent polarimeters at 43 GHz, coupled to a 1.5 m fully rotating crossed-Dragone telescope. A second frequency channel with six-elements at 95 GHz will be exploited as an atmospheric monitor. At present, most of the hardware of the STRIP instrument has been developed and tested at sub-system level. System-level characterization, starting in July 2018, will lead STRIP to be shipped and installed at the observation site within the end of the year. The on-site verification and calibration of the whole instrument will prepare STRIP for a 2-years campaign for the observation of the CMB polarization.
Wideband receivers for the 3-mm band were developed for CARMA, the Combined Array for Research in Millimeterwave
Astronomy. Three cryogenic MMIC (monolithic microwave integrated circuit) amplifiers manufactured in InP 35-
nm technology are combined in a block with waveguide probes and gain equalizers to cover the 80–116 GHz band.
These are followed by a sideband-separating mixer that has two 17 GHZ wide outputs, for upper and lower sidebands.
Each receiver has a feed horn followed by a circular-to-linear polarizer and orthomode transducer. The two polarizations
are amplified by the cryogenic MMICs, and the outputs downconverted in sideband separating mixers, resulting in four
1–18 GHz channels that can be simultaneously correlated. The first receiver was tested in the lab, and on-sky tests
conducted at CARMA. Measured noise temperatures were in the range 40–70 K, with a sideband rejection of about
We report on the development of Argus, a 16-pixel spectrometer, which will enable fast astronomical imaging over the 85–116 GHz band. Each pixel includes a compact heterodyne receiver module, which integrates two InP MMIC low-noise amplifiers, a coupled-line bandpass filter and a sub-harmonic Schottky diode mixer. The receiver signals are routed to and from the multi-chip MMIC modules with multilayer high frequency printed circuit boards, which includes LO splitters and IF amplifiers. Microstrip lines on flexible circuitry are used to transport signals between temperature stages. The spectrometer frontend is designed to be scalable, so that the array design can be reconfigured for future instruments with hundreds of pixels. Argus is scheduled to be commissioned at the Robert C. Byrd Green Bank Telescope in late 2014. Preliminary data for the first Argus pixels are presented.
We discuss the design and expected performance of STRIP (STRatospheric Italian Polarimeter), an array of coherent receivers designed to fly on board the LSPE (Large Scale Polarization Explorer) balloon experiment. The STRIP focal plane array comprises 49 elements in Q band and 7 elements in W-band using cryogenic HEMT low noise amplifiers and high performance waveguide components. In operation, the array will be cooled to 20 K and placed in the focal plane of a ~0.6 meter telescope providing an angular resolution of ~1.5 degrees. The LSPE experiment aims at large scale, high sensitivity measurements of CMB polarization, with multi-frequency deep measurements to optimize component separation. The STRIP Q-band channel is crucial to accurately measure and remove the synchrotron polarized component, while the W-band channel, together with a bolometric channel at the same frequency, provides a crucial cross-check for systematic effects.
A prototype heterodyne amplifier module has been designed for operation from 140 to 170 GHz using Monolithic Millimeter-
Wave Integrated Circuit (MMIC) low noise InP High Electron Mobility Transistor (HEMT) amplifiers. In the last few
decades, astronomical instruments have made state-of-the-art measurements operating over the frequency range of 5-100
GHz, using HEMT amplifiers that offer low noise, low power dissipation, high reliability, and inherently wide bandwidths.
Recent advances in low-noise MMIC amplifiers, coupled with industry-driven advances in high frequency signal interconnects
and in the miniaturization and integration of many standard components, have improved the frequency range and
scalability of receiver modules that are sensitive to a wide (20-25%) simultaneous bandwidth. HEMT-based receiver arrays
with excellent noise and scalability are already starting to be manufactured around 100 GHz, but the advances in technology
should make it possible to develop receiver modules with even higher operation frequency - up to 200 GHz. This
paper discusses the design of a compact, scalable module centered on the 150 GHz atmospheric window using components
known to operate well at these frequencies. Arrays equipped with hundreds of these modules can be optimized for many
different astrophysical measurement techniques, including spectroscopy and interferometry.
We report on the development of some of the key technologies that will be needed for a large-format Cosmic Microwave
Background (CMB) interferometer with many hundreds of wideband W-band (75-110 GHz) receivers. A scalable threebaseline
prototype interferometer is being assembled as a technology demonstration for a future ground- or space-based instrument.
Each of the prototype heterodyne receivers integrates two InPMonolithic Microwave Integrated Circuit (MMIC)
low-noise amplifiers, a coupled-line bandpass filter, a subharmonic balanced diode mixer, and a 90° local oscillator phase
switch into a single compact module that is suitable for mass production. Room temperature measurements indicate bandaveraged
receiver noise temperatures of 500 K from 85-100 GHz. Cryogenic receiver noise temperatures are expected to
be around 50 K.
The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new Earth remote sensing instrument
concept that has been under development at the Jet Propulsion Laboratory. First conceived in 1998 as a NASA New
Millennium Program mission and subsequently developed in 2003-2006 as a proof-of-concept prototype under the
NASA Instrument Incubator Program, it is intended to fill a serious gap in our Earth remote sensing capabilities −
namely the lack of a microwave atmospheric sounder in geostationary orbit. The importance of such observations have
been recognized by the National Academy of Sciences National Research Council, which recently released its report on
a "Decadal Survey" of NASA Earth Science activities. One of the recommended missions for the next decade is a
geostationary microwave sounder. GeoSTAR is well positioned to meet the requirements of such a mission, and because
of the substantial investment NASA has already made in GeoSTAR technology development, this concept is fast
approaching the necessary maturity for implementation in the next decade. NOAA is also keenly interested in GeoSTAR
as a potential payload on its next series of geostationary weather satellites, the GOES-R series. GeoSTAR, with its
ability to map out the three-dimensional structure of temperature, water vapor, clouds, precipitation and convective
parameters on a continual basis, will significantly enhance our ability to observe hurricanes and other severe storms. In
addition, with performance matching that of current and next generation of low-earth-orbiting microwave sounders,
GeoSTAR will also provide observations important to the study of the hydrologic cycle, atmospheric processes and
climate variability and trends. In particular, with GeoSTAR it will be possible to fully resolve the diurnal cycle. We
discuss the GeoSTAR concept and basic design, the performance of the prototype, and a number of science applications
that will be possible with GeoSTAR. The work reported on here was performed at the Jet Propulsion Laboratory,
California Institute of Technology under a contract with the National Aeronautics and Space Administration.
Recent developments in millimeter-wave receiver have enabled new remote sensing capabilities. MMIC circuits
operating at frequencies as high as 200 GHz have enabled low-cost mass producible integrated receivers suitable for
array applications. We will describe several ground-based demonstrations of this technology including development of
integrated spectral line receivers for atmospheric remote sensing, a synthetic thinned aperture radiometer for atmospheric
sounding and imaging and polarimetric array radiometers for astrophysics applications.
The Geostationary Synthetic Thinned Aperture Radiometer, GeoSTAR, is a new concept for a microwave atmospheric
sounder intended for geostationary satellites such as the GOES weather satellites operated by NOAA. A small but fully
functional prototype has recently been developed at the Jet Propulsion Laboratory to demonstrate the feasibility of using
aperture synthesis in lieu of the large solid parabolic dish antenna that is required with the conventional approach.
Spatial resolution requirements dictate such a large aperture in GEO that the conventional approach has not been
feasible, and it is only now, with the GeoSTAR approach, that a GEO microwave sounder can be contemplated.
Others have proposed GEO microwave radiometers that would operate at sub-millimeter wavelengths to circumvent the
large-aperture problem, but GeoSTAR is the only viable approach that can provide full sounding capabilities equal to or
exceeding those of the AMSU systems now operating on LEO weather satellites and which have had tremendous impact
on numerical weather forecasting. GeoSTAR will satisfy a number of important measurement objectives, many of them
identified by NOAA as unmet needs in their GOES-R pre-planned product improvements (P3I) lists and others by
NASA in their research roadmaps and as discussed in a white paper submitted to the NRC Decadal Survey. The
performance of the prototype has been outstanding, and this proof of concept represents a major breakthrough in remote
sensing capabilities. The GeoSTAR concept is now at a stage of development where an infusion into space systems can
be initiated, either on a NASA sponsored research mission or on a NOAA sponsored operational mission. GeoSTAR is
an ideal candidate for a joint "research to operations" mission, and that may be the most likely scenario. Additional
GeoSTAR related technology development and other risk reduction activities are under way, and a GeoSTAR mission is
feasible in the GOES-R/S time frame, 2012-2014.
The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new concept for a microwave sounder, intended to be deployed on NOAA's next generation of geostationary weather satellites, GOES-R. A ground based prototype has been developed at the Jet Propulsion Laboratory, under NASA Instrument Incubator Program sponsorship, and is currently undergoing tests and performance characterization. The initial space version of GeoSTAR will have performance characteristics equal to those of the AMSU system currently operating on polar orbiting environmental satellites, but subsequent versions will significantly outperform AMSU. In addition to all-weather temperature and humidity soundings, GeoSTAR will also provide continuous rain mapping, tropospheric wind profiling and real time storm tracking. In particular, with the aperture synthesis approach used by GeoSTAR it is possible to achieve very high spatial resolutions without having to deploy the impractically large parabolic reflector antenna that is required with the conventional approach. GeoSTAR therefore offers both a feasible way of getting a microwave sounder in GEO as well as a clear upgrade path to meet future requirements. GeoSTAR offers a number of other advantages relative to real-aperture systems as well, such as 2D spatial coverage without mechanical scanning, system robustness and fault tolerance, operational flexibility, high quality beam formation, and open ended performance expandability. The technology and system design required for GeoSTAR are rapidly maturing, and it is expected that a space demonstration mission can be developed before the first GOES-R launch. GeoSTAR will be ready for operational deployment 2-3 years after that.
The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new microwave atmospheric sounder under development. It will bring capabilities similar to those now available on low-earth orbiting environmental satellites to geostationary orbit - where such capabilities have not been available. GeoSTAR will synthesize the multi-meter aperture needed to achieve the required spatial resolution, which will overcome the obstacle that has prevented a GEO microwave sounder from being implemented until now. The synthetic aperture approach has until recently not been feasible, due to the high power needed to operate the on-board high-speed massively parallel processing system required for 2D-synthesis, as well as a number of system and calibration obstacles. The development effort under way at JPL, with important contributions from the Goddard Space Flight Center and the University of Michigan, is intended to demonstrate the measurement concept and retire much of the technology risk. To that purpose a small ground based demo version of GeoSTAR is being constructed, which will be used to characterize system performance and test various calibration methods. This prototype development, which is being sponsored by NASA through its Instrument Incubator Program, will be completed in 2005. A GeoSTAR space mission can then be initiated. In parallel with the technology development, mission architecture studies are also under way in collaboration with the NOAA Office of System Development. In particular, the feasibility of incorporating GeoSTAR on the next generation of the geostationary weather satellites, GOES-R, is being closely examined. That would fill a long standing gap in the national weather monitoring capabilities.