Detector and instrument system development at JPL is primarily aimed at creating technologies to enable the scientific and engineering measurements needed to accomplish NASA’s science goals. This is an ongoing effort, with major overarching challenges to reduce power, volume, mass, noise and complexity while increasing sensitivity and data-rate capabilities. Future development goals are to advance onboard electronics, processing and autonomy to reduce data-rate requirements and improve instrument capability and mission throughput. Areas of strategic focus include:
- Detectors and focal plane systems that push performance to physical limits while maintaining sensitivity and allowing precision spaceborne calibration
- Active remote sensing that probes environments using radio-frequency radars, GPS signals and laser-based ranging, absorption and spectroscopic systems
- Passive remote sensing that incorporates the relevant optics, detectors and heterodyne techniques to provide cameras, spectrometers, radiometers and polarimeters across most of the electromagnetic spectrum; as well as submillimeter imaging arrays, hyperspectral imaging systems and atomic quantum sensors
- In-situ sensing that probes the state and evolution of Solar System bodies by investigating physical properties, morphology, chemistry, mineralogy and isotopic ratios, as well as by searching for organic molecules and for evidence of previous or present biological activity
- Active cooling systems for detectors and instruments that provide measurements with an adequate signal-to-noise ratio and that are integrated with the detection system rather than standing separate
Progress in these areas, which encompass an especially broad set of technologies, requires specialized facilities such as JPL's Microdevices Laboratory for fundamental device research, as well as for the development of novel, flight proven detectors and instruments that enhance NASA’s missions and are not available elsewhere.
Active Research Thrusts
Detectors and Focal Plane Array Systems
Detectors and focal plane array systems are central to scientific measurements across a wide range of the electromagnetic spectrum and generally require optimization for the expected signal frequency wavelength and levels.
The signals of interest can be exceedingly weak, barely above noise levels, and these detectors and focal plane arrays must be designed and engineered to reduce noise to theoretical physical limits, maintain sensitivity across the requisite detection bandwidth and allow precision calibration in the space environment. Driven by NASA science and optical telecommunication goals, the detectors and focal planes developed by JPL operate over bands and at sensitivity levels not available in commercial systems, thus requiring in-house development.
Active Remote Sensing
JPL actively develops a variety of instruments for active remote sensing, including radar and laser spectroscopy. The laboratory has extensive experience in developing and integrating radar technologies to meet scientific measurement requirements. For example, the NASA Spaceborne Imaging Radar/Synthetic Aperture Radar was the first and only SAR that was fully polarimetric at C-band and L-band, with independent horizontal and vertical channels for independent steerability, as well as phase scanning in elevation and limited phase scanning in azimuth.
Laser absorption spectroscopy systems, such as the tunable laser spectrometer (TLS), and laser-induced- breakdown spectroscopy (LIBS) systems on Mars Science Laboratory (MSL) are in common scientific use. LIBS systems have demonstrated meter-range standoff measurements. LIBS systems for quantitative analysis in high-atmospheric-pressure regimes such as Venus and Titan are being developed by JPL to meet scientific needs from a static lander.
Passive Remote Sensing
JPL is a world leader in developing passive remote sensing systems. Currently under development are far-infrared spectrometers that are sensitive enough for background-limited operation on cold space telescopes. Also under development are solar-occultation Fourier transform infrared (FTIR) spectrometers that will seek trace gases in planetary atmospheres. The laboratory is also developing array formats with thousands of detectors that provide high system sensitivity in multiple observing bands to take advantage of the large gains possible with cryogenic telescopes; these developments include significant multiplexing improvements and high-yield fabrication processes to realize fundamental sensitivity limits.
3-D hyperspectral-imaging and imaging-spectrometer systems, which simultaneously map the full field-of-view onto the spectrometer, are a key instrument technology in which JPL is leading the field. These systems improve signal-to-noise ratio through spatial multiplexing, eliminating the need to perform “push-broom” scanning required by existing space-borne spectral imagers, thereby enabling mission operations and designs that are simpler and more flexible. Recent systems, such as the Moon Mineralogy Mapper (M3), provide high-quality scientific data on-orbit. Optically faster, high uniformity systems for outer planet missions are now in development that will enable spectroscopy in the image domain while spanning wide spectral ranges from the ultraviolet to the thermal infrared.
Hyperspectral imaging technology is advancing the state-of-the-art in astrophysics, particularly in observations of extrasolar planets, galaxies and other faint sources. The application of 3-D hyperspectral imaging to planetary missions will lead to exciting advancements in areas such as characterizing cloud/atmospheric/aerosol structure and dynamics, surface composition and mineralogy, surface morphology and detection of volcanism and hot spots.
Another of JPL’s most important and successful product line instruments is the remote-sensing multi-sensing thermal imager (TI). The JPL TI has been selected for Mars Reconnaissance Orbiter (the MCS instrument) and Lunar Reconnaissance Orbiter (the Diviner instrument), and could be an important instrument on the Europa Clipper mission concept that currently is being developed. The enabling technology for these thermal imagers is the uncooled microthermopile arrays developed at the laboratory’s Microdevices Laboratory. JPL is currently developing new arrays of thermopiles with format sizes 100 times larger than the arrays flying on MCS and Diviner. These large arrays will lead to new power filter and grating radiometers for a wide range of space-borne missions from long-term Earth climate studies to studies of Jupiter Trojans and other primitive bodies throughout the solar system.
Finally, JPL is developing and maturing space-qualified, small atomic clocks that are approximately 1 liter in volume and 1 kilogram in mass, with a frequency stability of 10-15. Future space optical clocks of superior performances are also being developed. Highly accurate clocks and sensitive quantum sensors will find game-changing applications in deep space interplanetary network operation, earth science, planetary science and fundamental physics including gravitational wave detection.
JPL has conducted spaceborne investigations of all the planets in our solar system and is now focused on lander missions to conduct detailed surface and subsurface studies that cannot be accomplished remotely from space. These studies require instruments that can operate in-situ to investigate physical properties, morphology, chemistry, mineralogy, isotopic ratios and search for evidence of previous or present biological activity.
The instruments developed for flights after 2020 will dramatically extend “lab-on-a-chip” technology with microfluidics, subcritical extraction and electrophoresis.
JPL has developed a microfluidic microchip, often called a lab-on-a-chip, for completely automated end-to-end microchip capillary electrophoresis (μCE) analysis. The process involves manually placing a sample of amino acids is on the surface of a microchip, but all subsequent steps (automated labeling, dilution, spiking and amino acid separation) are performed under computer control without further user intervention.
Active Cooling Systems for Detectors and Instruments
Many instruments, such as those that deal with infrared astronomy and Earth science, must be actively cooled to provide measurements with an adequate signal-to-noise ratio. Efficiency is paramount for the crycoolers used for these missions. JPL is currently investing in technology development for increased thermodynamic efficiency in the low-temperature stages of mechanical cryocoolers, through improved regenerator structures and materials, and with active pressure-mass phase-shifting techniques.