Harris is currently developing different types of imaging hyperspectral instruments for CubeSat and other small satellite applications. All of these instruments utilize Fourier Transform Spectrometer (FTS) interferometer technology, which has been proven on larger space instruments for NASA and NOAA. Most of these instruments are aimed at remote sensing of the earth from low orbit. One example is HyperCube™, which is a hyperspectral mid-wave infrared (MWIR) instrument compatible with 6U CubeSats capable of collecting vertical moisture profiles and three-dimensional winds in the earth’s atmosphere. Another example is Harris’ HyperStare, which is a larger-aperture imaging FTS instrument that provides improved sensitivity and spatial resolution for detection of trace greenhouse gases in the atmosphere. This paper will provide design summaries and performance capabilities of each of these new instrument types. It will also discuss Harris’ newly developed ground station capability for operating small constellations of small satellites. In addition, new FTS technologies that may be suitable for future small satellites will be discussed.
In this paper, a new wave front sensor design that utilizes the benefits of image projections is described and analyzed. The projection-based wave front sensor is similar to a Shack-Hartman type wave front sensor, but uses a correlation algorithm as opposed to a centroiding algorithm to estimate optical tilt. This allows the projection-based wave front sensor to estimate optical tilt parameters while guiding off of point sources and extended objects at very low signal to noise ratios. The implementation of the projection-based wave front sensor is described in detail showing important signal processing steps on and off of the focal plane array of the sensor.
In this paper the design is tested in simulation for speed and accuracy by processing simulated astronomical data. These simulations demonstrate the accuracy of the projection-based wave front sensor and its superior performance to that of the traditional Shack-Hartman wave front sensor. Timing analysis is presented which shows how the collection and processing of image projections is computationally efficient and lends itself to a wave front sensor design that can produce adaptive optical control signals at speeds of up to 500 hz.
The crosstrack IR Sounder (CrIS) is one of the key sensors now under development for the National Polar-orbiting Operational Environmental Satellite System program, which is the follow-on to the current DMSP and POES meteorological satellite systems. CrIS is a interferometric sounding sensor which accurately measures upwelling earth radiances at very high spectral resolution, and uses this data to construct vertical profiles of atmospheric temperature, moisture and pressure. These profiles are also called Environmental Data Records, or EDRs. The purpose of this paper is to describe the top level trade studies that led to the selection of the overall CrIS sensor design. Most of these trade studies involved a tradeoff between system performance and relative system cost. This paper discusses how EDR performance was determined for different trade study options, and review the key design and cost tradeoffs that led to the selection of the CrIS design.
It is important in any remote sensing radiometer to identify and characterize the noise and error sources of the radiometer. At ITT, we have produced a number models to characterize noise and its impacts. The latest noise model is for the Cross-track Infrared Sounder (CrIS) instrument which is part the National Polar-orbiting Operational Satellite System (NPOESS). The required accuracy of the instrument demands identifying and characterizing the noise and random error sources to lower the risk of poor instrument performance. This paper lists the sources of noises and random errors identified in the CrIS sensor and compares model predictions to measurements from the first CrIS Engineering Development Unit (EDU).
In this presentation we describe flight results for an airborne IR hyperspectral imager used as a test bed for LEISA, a compact spaceborne wedged filter spectrometer. The moderate spectral resolution Linear Etalon Imaging Spectral Array (LEISA) is a low-mass, low-power, low-cost infrared spectral imager for spacecraft applications. LEISA uses a state-of-the- art wedged infrared filter (a linear variable etalon, LVE) in conjunction with a detector array to obtain hyperspectral image cubes. The LEISA concept has been described previously in Reuter et al., 1997, SPIE Vol. 2957, pp 154 - 161, 'EUROPTO Conference on: Advanced and Next-Generation Satellites II.,' 23 - 26 September, 1996, Taormina, Italy. A LEISA type instrument, the Atmospheric Corrector (LAC), will fly on NASA's EO-1 spacecraft to be launched in Dec. 1999. The airborne version of LEISA covers the spectral region from 1.0 to 2.5 microns at a constant resolving power ((lambda) /(Delta) (lambda) ) of approximately 250 (i.e. 4 nm 1.0 microns and 10 nm 2.5 microns). The single pixel spatial resolution is 2 milliradians. This corresponds to 2 meters 1 km altitude and 20 meters 10 km. The instrument has been operated throughout this altitude range. The instrument has a swath width of approximately 29 degrees. A 256 X 256 element NICMOS (Near Infrared Camera Multi-Object Spectrometer) HgCdTe detector array is used as the focal plane. The focal plane is enclosed in a small cryogenic dewar at liquid Nitrogen temperature. Results will be presented for three series of airplane flights: Lubbock Texas (USA) June - September 1997, Lubbock Texas (USA) July - September 1998, Bethlehem Orange Free State (South Africa) March 1999. Issues to be discussed include pre-, and post-flight calibration, image registration and spectral image reconstruction. The relationship of these measurements to future spaceborne hyperspectral imagers will also be discussed.
The technique of integral projections is used to perform co- registration of data from a wedge spectrometer instrument that has been developed by NASA Goddard Space Flight Center. The spectrometer is currently being flown on a plane and operates in the 1 - 2.5 micron range. The technique involves a number of steps. First, an algorithm was developed to calculate the absorption bands that occur within the spectral region. At this point the method of Integral Projections is used to vectorize the image. The Integral Projections method performs a number of key functions in the registration process: increases SNR, reduces affects of spatial non-uniformities within the data, and results in a much faster algorithm since the operation is on vectors. The final step is to register the zero crossing of the second derivative of the vectors. Two issues encountered with co-registration is dealing with the absorption bands that occur within the spectral region of interest and the multiple problem of recognizing features that are not only shifting in x and y but also appear different at different wavelengths. Results will be presented in which the application of our algorithm obtains the appropriate x,y shifts necessary to reconstruct a registered data cube.