2008 ACT Projects Awarded

A significant number of the Earth Science missions utilize active remote sensing, which requires considerable power-aperture product to meet the science objectives. These include:  ICESatII, DENDynI, ASCENDS, ACE, LIST, 3D Winds, and GACM.  This provides the mission engineer with a new capability to trade large apertures, which are currently unaffordable, against large, expensive laser power.  Mission design studies have demonstrated that upwards of 3 meters of aperture can be accommodated in a mid-class launch vehicle, whereas past efforts have been limited to 1 meter. This technology also enables new configurations of multiple telescopes as an alternative to large scanning telescopes, and their attendant challenges to the spacecraft.  In addition, there are passive missions which require large apertures, for which deployable telescopes have been considered, but which are expensive.

ITT has developed and demonstrated the cost, time and mass advantages of the ‘corrugated mirror’ technology using internal funds.  ITT has also partnered with NASA under the IPP to test a corrugated mirror under cryogenic conditions. However, these systems are optically slow (f/4) and do not enable the widest range of missions and benefits to NASA that are possible. This effort will demonstrate that the significant cost, schedule and mass advantages of the corrugated technology can be maintained when manufacturing optical fast (f/1.2) systems, which are required to enable the most compact packaging, and thus the largest area for the smallest launch vehicle. This effort will produce an f/1.2 – 0.5 meter diameter mirror and corresponding compact telescope design, suitable for ASCENDS and similar active missions.

This NGRT will be implemented by leveraging and integrating several recently developed material technologies. These newly developed material technologies include Shape Memory Polymer (SMP) material, high-precision Membrane Shell Reflector Segment (MSRS) casting process, near zero CTE membrane material Novastrat [Poe, 2006], and PVDF electro-active membrane [Fang et al., 2007]. The architecture of this NGRT has a number of high precision MSRSs supported by a SMP tetrahedral truss to form a reflector. A tetrahedral truss offers almost one order of magnitude higher precision than any currently used tensioning cable truss [Hedgepeth, 1982] and can provide a very irregular surface contour (e.g. dual-frequency surface for ACE) that is extremely difficult, if not impossible, for a tensioning cable truss. Compared to the big loss and scattering of the high-frequency RF signal caused by currently used mesh reflective surface, MSRSs form a high definition, smooth and continuous surface to assure very high gain for high RF frequencies.

This project will last for three years and increase the TRL from 2 at entry to 4 at exit.

With an entry TRL of 3 and a planned exit of 5 over a three year period of performance, we will model, design, fabricate, and test the phased array tile.

We propose to take the BATC time-domain polarization scrambler (TDPS), demonstrated under BATC funding, to a higher TRL. The TDPS uses high frequency polarization modulation to provide a large number of polarization cycles during a typical imaging integration time, producing a net null polarized beam. The laboratory demonstration unit will be further characterized and evolved, with the aim of incorporating a TDPS into an operating spectrometric system. The objective of the program is to produce a unit that is small and rugged enough to operate in a fieldable UV, Visible or Infrared spectrometer, the PolZero TDPS. A goal of the program is to use a TDPS-enhanced spectrometer in a mobile (possibly aircraft-based) Earth observation field measurement. The TRL of the TDPS will be advanced from TRL 3 (laboratory demonstration) to TRL 5 (demonstration in simulated operational environment) in a two year program.

The technology developed under this ACT program is relevant to UV/VIS spectrometers for ocean color and ozone measurements in particular and UV/VIS/NIR spectrometers and multi-spectral instruments in general.  The depolarizer has application on GEOCAPE, GACM, HyspIRI, and ACE.

Based on our successful experience in the design and build of a prototype 256×256 AlGaN array we will first scale this design up to a standard 1024×1024 18 um pixel pitch array appropriate for high spatial/spectral resolution sensors operating in the 270-365 nm range. We will then design and build a 1024×1024 InGaN array which will operate in the 365-480 nm range. Both focal planes will undergo full radiometric characterization and will be incorported into a laboratory spectrograph for demonstration and comparative testing. The period of performance of the proposed work is January 2009 to January 2012 with TRL maturation from level 2 to level 4.

We propose to construct and demonstrate an efficient, photon-counting detection system capable of simultaneously providing information about aerosol loading and motion.  This detection system will ultimately become part of a lidar system for cloud-aerosol transport studies.  In the long term, we want to construct and demonstrate a Cloud-Aerosol Transport System (CATS) lidar.  The CATS lidar will be inherently a cloud-aerosol backscatter lidar but will also provide information on cloud and aerosol height, internal structure, and optical properties (e.g., optical depth).  The added capability to derive wind motion will enable studies of aerosol transport and cloud motion.  The technology developed will have direct application to future spaceborne missions, such as the proposed Aerosol-Cloud-Ecosystems (ACE) mission, and will provide critical validation capability for future missions.  The technology also has potential application to the 3-D winds mission, but our focus is on the nearer-term ACE mission.

The basis for the detection system is a novel holographic optical element developed at NASA-Goddard.  Previous investments from ESTO, SBIR, and Goddard IRAD will be leveraged to permit construction of a cost effective yet highly advanced detector subsystem suitable for future inclusion into a CATS lidar instrument.  Our goal is to utilize future opportunities, such as the Instrument Incubator Program, to build the CATS aerosol-based lidar for use onboard a high-altitude aircraft to provide demonstration of both technology and measurements.

The proposed Far-Infrared Extended Blocked Impurity Band (FIREBIB) detectors are an extension of the well-known class of silicon BIB detectors for the mid-infrared. We will extend the wavelength into the far-IR to at least 50 um (goal 100 um) using the recently demonstrated approach. We will also adapt a detector design and light-trapping detector packaging from another recent detector program to achieve the following target performance levels from 10 to 50 um (with 100 um goal): (i) Unity gain; (ii) Bandwidth > 100 kHz suitable for the CLARREO Fourier transform spectrometer instruments; (iii) Quantum Efficiency (QE) > 99.9% in a trap detector configuration; (iv) Specific Detectivity > 1e+10 cm sqrt(hz) /W (goal > 1e+11 cm sqrt(hz)/W); (v) QE stability against temperature and radiation effects; (vi) Nominal Detector Area (trap acceptance area) of 200 x 200 µm2. These enhancements in detector performance will enable improvements in overall system performance in terms of increased radiometric accuracy, reduced spatial smearing, and simpler calibration approaches for CLARREO.

We accomplish this component technology advance in two steps.  First we demonstrate 5W laser transmitter output power in the lab, cost-effectively leveraging an existing LM commercial METEOR® 2-µm single frequency laser, proven 2-µm COTS fiber amplifier technology, and LM’s high-precision frequency control technology.  Then we demonstrate 5W transmitter output power again, but featuring the <1MHz absolute frequency locking that we demonstrated in the airborne prototype and that is needed to meet required CO2 measurement precision on ASCENDS.  Secondary objectives include advancing space readiness of a few critical components unique to the CLASS instrument by completing space environment characterization testing, as well as refinement of our point-of-departure instrument design and performance model predictions for CLASS manifested on ASCENDS.

We advance CLASS instrument space-readiness from TRL3+ to TRL4 in year 2 and to just shy of TRL5 in year 3.  As a result, we ready CLASS as a leading candidate sensor for ASCENDS, featuring non-cryogenic detectors, broad optical pump bands, relaxed thermal rejection needs, all-fiber amplifier assembly, and integrated pump diode redundancy.

An innovative in-pixel current-to-frequency digitization approach will be demonstrated using conventional 0.35 um process circuit design tools proven to successfully develop similar circuits.  The resulting 128×128 ROIC design will be fabricated by a commercial foundry and the chips produced will be tested in the JPL CMOS Image Sensor development labs.

To demonstrate ROIC performance in a relevant environment (i.e. an imaging spectrometer), final testing will be done by substituting our ROIC for the detector in the Fourier Transform UV/Vis Spectrometer (FTUVS) at JPL’s Table Mountain Facility which is an operational instrument, routinely measuring total column abundances of OH, NO2, NO3, CO2, BrO and other species.  Comparing the ROIC spectra with those normally produced by FTUVS, will demonstrate the utility of the ROIC for atmospheric composition measurements called for in the Decadal Survey.

A three year effort will advance ROIC technology from the current TRL level 2, to the planned exit level of TRL 5.

In the work described in this proposal, we will explore these two alternative approaches through the construction of a Ka-band receiver with implementations of both direct and two-stage downconverted signals, and provide metrics of power and performance as a function of the design spaces.  The final product will be directly integrable into the overall SWOT instrument architecture.

A stable platform for the arrays is a critical part of making a radar-mapping mission successful, since the SWOT instrument requires tight pointing requirements and stability in order to meet its mission goals.  These requirements can be met in part by minimizing the equipment on the ends of the interferometric mast, but significant challenges remain in designing a stiff, stable antenna deployment structure that can package down into a small space for launch.

Over a period of three years, this task will develop the requirements needed to build a prototype of the deployment mechanism, then design, build, and test the mechanism.  This will be done in stages; starting with analysis and design to raise the TRL and understanding in one year, followed by a two year build and test to further raise the TRL level.  In addition, valuable models will be created to predict the performance of such a system when the flight unit is built.  Building upon the experience of previous work, such as the Wide-Swath Ocean Altimeter (WSOA), this task will move the TRL of the device from level 2 to level 4.