Laser remote sensing of the Earth from space offers many unique capabilities stemming from the unique properties of
lasers. Lidars make possible three-dimensional characterizations that enable new scientific understanding of the natural
processes that shape the planet's oceans, surface, and atmosphere. However, the challenges to further expand on these
successes remain complex. Operation of lidars from space is limited in part by the relatively low power available to the
lasers, the low signal scattered back to the instrument because of the large distance to the surface, and the need for
reliable and autonomous operation because of the significant investment required for satellites. The instrument
complexities are compounded by the diversity in the Earth scenes as well as the variability in albedo from cloud, ice,
vegetation, desert, or ocean, combined with the highly variable transmission of the laser beam through clouds, forest
canopy, or ocean surface and near-surface. This paper will discuss the development of a new approach to space-based
lidars that uses adaptive instrument techniques to dramatically enhance the capability of space-based lidars.
Meteorological sounding data provided by atmospheric imaging sounders have applications in weather forecasting,
atmospheric chemistry, and climate monitoring. Realistic scenes for these instruments vary in both spatial and spectral
content and such variations can impact the radiometric performance of these instruments. As sounders are developed to
provide climate records with demanding long-term radiometric accuracy requirements, it becomes increasingly
important to understand the effect of scene variations on the performance of these instruments. We have examined the
noise performance and radiometric accuracy of two geostationary sounder architectures in cloudy scenes: a Fourier
transform spectrometer (FTS) and a dispersive spectrometer. Factors such as stray light, ghosting, scattering, and line-ofsight
jitter in the presence of scene inhomogeneities are considered. For each sounder architecture, quantitative estimates
of the radiometric errors associated with sounding in cloudy scenes are made. We find that in a dispersive system the
dominant error in a cloudy scene originates from ghosting within the instrument, while in an FTS the dominant error
originates from scene modulation created by line-of-sight jitter in a partially cloudy scene coupling into signal
modulation over the scale of the changing optical path length of the interferometer. In this paper we describe the
assumptions made and the modeling performed. We also describe how each factor influences the radiometric
performance for that architecture.
The Topographic Mapping Flash Lidar (TMFL) developed at Ball Aerospace combines a pushbroom format transmitter
at 1064 nm with a flash focal plane receiver. The wide 20 degree field of view of the instrument enables broad swath
coverage from a single laser pulse without the need for a scanning mechanism. These features make the TMFL design
particularly well-suited for space flight. TMFL has been demonstrated during an airborne flight where data were
gathered over a forest plot to measure tree waveforms. Topographic maps were assembled of river beds and geologic
areas of high relief. The TMFL has also been used to observe multiple-scattering phenomena in clouds by illuminating a
steam plume from the aircraft above. Signal was recorded off-axis from the illuminated laser line by as much as 1
degree. The TMFL study of multiple-scattering is valuable as it provides a unique way to significantly improve the
calibration of measured backscatter for space lidars. Lidar backscatter was also measured from water surface and was
shown to correlate with models of water surface roughness.
The Airborne Sensors Initiative (ASI) at Ball Aerospace and Technologies Corp. (BATC) specializes in airborne
demonstration of internally-developed instrument concepts and innovative remote sensing technologies. In December
2006, ASI flew an environmental remote sensing suite consisting of the Low Light Imager (LLI) and Prototype Airborne
Visible Imaging Spectrometer (PAVIS), both of which are operated using a pushbroom approach. LLI is designed for
nighttime or high dynamic range imaging. It is capable of yielding 107 dynamic range and offers quality images amid
illumination extending from a 1/4 moon to full sunlight and with autonomous operation. PAVIS is an imaging
spectrometer based on the Dyson design and exhibits a 200 nm spectral bandwidth tunable within 400 − 850 nm.
Developed internally to demonstrate promising remote sensing capabilities, these small, low-mass and low-power
instruments are prepared for aircraft flight and are currently being used in the field to acquire scientific data. The
LLI/PAVIS instrument suite has been utilized to collect airborne urban and rural imagery, as well as spectral information
about the Great Salt Lake area, western Colorado, and ancient lava flows in southern Idaho. Highlights of the instrument
design and ensuing data from previous flights are presented herein.
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