The Ocean Color Instrument (OCI) on NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem mission is a hyperspectral imager with high SNR, precision and dynamic range, and with a very low striping artifact level in the 342-887 nm wavelength range with a spectral resolution of 5 nm in 2.5 nm steps, providing a significant technological advancement over previous ocean imagers. To achieve this, OCI is designed with specialized optical imaging and opto-electronic detection systems that push the boundaries of several state-of-the-art technologies. This paper provides an overview of these systems together with their achieved performances and discussions of their key design challenges.

Over the past 40 years, satellite ocean color remote sensing has evolved from the demonstration Coastal Zone Color Scanner sensor with three bio-optical spectral bands to hyperspectral sensors like the Hyperspectral Imager for Coastal Ocean and the Ocean Color Imager (>90 spectral bands) planned for the NASA PACE mission. This increase in spectral coverage has been the result of scientific advances in ocean optics, marine biogeochemistry, and bio-optical algorithms for greater insight into the global carbon cycle, marine ecosystem structure, and anthropogenic impacts on the marine environment expand. As a result, instrument designers and engineers have leveraged off developments in optics, detector systems, electronics, and other technologies to derive new designs that meet increasingly stringent performance requirements, e.g., signal-to-noise ratios, and spectral, spatial, and temporal coverages. In this chapter, the evolution in science and sensor requirements, the lessons learned from specific heritage sensors, sensor calibration, and characterization considerations, and some fundamentals of satellite sensor engineering are reviewed.

The Ocean Radiometer for Carbon Assessment (ORCA) is a new design for the next generation remote sensing of oceans biology and biogeochemistry satellite. ORCA is configured to meet the requirements of the Decadal Survey recommended Aerosol, Cloud, and Ecology (ACE), the Ocean Ecosystem (OES) radiometer and the Pre-ACE climate data continuity mission (PACE). Under the auspices of a 2007 grant from NASA's Research Opportunity in Space and Earth Science (ROSES) and the Instrument Incubator Program (IIP), a team at the Goddard Space Flight Center (GSFC) has been working on a functional prototype of a hyperspectral imager with flightlike optics and scan mechanisms. This paper discusses the requirements and optomechanical design of this prototype.

In this paper, recently developed dual polarization 643 GHz and single polarization 874 GHz receivers for airborne CoSSIR, Compact Scanning Sub-millimeter wave Imaging Radiometer were utilized for ice cloud measurements. The results show that the brightness temperature map clearly demonstrates the recent advance in sub-millimeter wave radiometry for ice cloud sensing. The 874 GHz radiometer greatly improves the CoSSIR sensitivity to small ice particles. This implies that CoSSIR is able to pick up the measurements of ice clouds where the visible and inferred approaches left behind, i.e. saturated. The polarization measurement capability at 643 GHz can provide information on particle shapes, as well as improve the accuracy of the ice cloud parameters retrievals, e.g., ice water path and particle size.

Previous water vapor profiling by millimeterwave radiometry using the 183-GHz absorption line is generally limited to an altitude range of 0-11 km. The additional measurements at the frequencies of 380.2 0.8, 380.2 1.8, 380.2 3.3, and 380.2 6.2 GHz by the new airborne compact scanning submillimeterwave imaging radiometer (CoSSIR) reported in this paper can extend this profiling capability up to an altitude of about 15 km. This is demonstrated by recent CoSSIR measurements onboard the NASA WB-57 aircraft in a flight from Texas to Costa Rica on January 14, 2006. Retrievals of water vapor mixing ratio were performed at eight altitudes of 1, 3, 5, 7, 9, 11, 13, and 15 km from the CoSSIR data set acquired at observational angles of 0 and 53.4. The results were compared with other available measurements from near-concurrent satellites. A very good agreement was found between the collocated values of total precipitable water (TPW) derived from the CoSSIR-retrieved water vapor profiles and those estimated from Tropical Rainfall Measuring Mission Microwave Imager; the average TPW differences range between 0.30 and 0.64 cm, depending on CoSSIR's observational angles. The accuracy of the retrievals was inferred from an analysis of inflight CoSSIR radiometric signal fluctuations.

In this paper, recently developed dual polarization 643 GHz and single polarization 874 GHz receivers for airborne CoSSIR, Compact Scanning Sub-millimeter wave Imaging Radiometer were utilized for ice cloud measurements. The results show that the brightness temperature map clearly demonstrates the recent advance in sub-millimeter wave radiometry for ice cloud sensing. The 874 GHz radiometer greatly improves the CoSSIR sensitivity to small ice particles. This implies that CoSSIR is able to pick up the measurements of ice clouds where the visible and inferred approaches left behind, i.e. saturated. The polarization measurement capability at 643 GHz can provide information on particle shapes, as well as improve the accuracy of the ice cloud parameters retrievals, e.g., ice water path and particle size.

The US/Japan Tropical Rainfall Measuring Mission has led to the initiation of a new international satellite precipitation mission, the Global Precipitation Measurement (GPM) mission, to be led primarily by NASA and NASDA. One of the main objectives of GPM is high frequency global sampling of rainfall. Our work develops passive microwave radiometer technology that is suitable for high quality rain measurement but is also lightweight and low power, and follows a technology path that leads to significantly reduced per unit recurring costs. Taken together, these improvements will permit multiple sensors to be flown in a constellation of small satellites, thereby increasing the sampling frequency of global precipitation.

The X-Band Lightweight Rainfall Radiometer using synthetic thinned aperture radiometer technology (LRR-X STAR) is an aircraft microwave sensor that is jointly under development by the NASA Goddard Space Flight Center and the University of Michigan. It operates at 10.7 GHz with 86+ simultaneous 2.1/spl deg/ HPBW antenna beams distributed over a /spl plusmn/ 45/spl deg/ cross track field of view to permit pushboom imaging. It is intended to address several pressing issues related to the Global Precipitation Measurement (GPM) Mission, for which it is a science and technology testbed instrument. In terms of technology readiness, LRR-STAR will evaluate and validate the design approaches being taken by each of its critical subsystems. At the system level, it will validate the calibration methodology used to produce Level 1 brightness temperature imagery. All electrical, mechanical and thermal subsystems of the LRR-STAR are currently in development and several key subsystems have had successful prototype fabrication and laboratory testing. An overview of the instrument design is presented, together with a status report on the hardware development.

Band averaged absorption coefficients are presented for the wavelength bands of the Nimbus-7 Solar Backscattered Ultraviolet (SBUV) and Total Ozone Mapping Spectrometer (TOMS) experiments, and the Nimbus-4 Backscattered Ultraviolet experiment using the recent laboratory ozone cross-section measurements at the U.S. National Bureau of Standards (NBS) by A. Bass and R. Paur being presented at this symposium. Also, coefficients for the Dobson bands are presented. The new coefficients based on the NBS data are compared with coefficients computed using earlier laboratory absorption measurements. For total ozone, we present the biases which will result if these new coefficients are adopted by IOC and used by the Dobson and satellite networks.

Recent satellite experiments have produced a large multi-year data base of stratospheric ozone profiles covering the entire globe. Among these, the Solar Backscatter Ultraviolet Experiment (SBUV) has been operating continuously since November 1978 providing some 1000 profiles per day. Based on detailed comparisons with ozonesondes and other satellite based instruments, SBUV data have been determined to be of excellent quality from about 50 km down to the tropopause.