THE FUTURE OF U. S. COMMERCIAL REMOTE SENSING FROM SPACE*

R. F. Heidner III, Distinguished Scientist J. M. Straus, Executive Vice President The Aerospace Corporation P.O. Box 92957 Los Angeles, CA 90009 [email protected] [email protected]

ABSTRACT

The Land Remote Sensing Policy Act of 1992 authorizes U.S. firms to seek licenses for privately operated, space based land remote sensing systems. NOAA was delegated the authority to issue such licenses after appropriate consultation with other affected agencies. In 1994, PDD-23 offered additional guidance and encouragement for these private initiatives. Since 1993, NOAA has issued more than 20 such licenses, and four systems are currently operating. Economic viability forecasts for the U.S. “commercial” remote sensing (CRS) industry have varied widely. Most were overly optimistic, owing in part to the long history of remote sensing from space being the sole province of governments; complex economic and geopolitical forces influence the search for commercial applications and the servicing of global markets. NSPD- 27, U.S. Commercial Remote Sensing Space Policy (April 25, 2003) recently replaced PDD-23. Its language more forcefully advocates USG use of CRS space data, products and services; several such initiatives are currently in place. This presentation examines the nature of remote sensing information that can be acquired by space systems and offers judgments about the commercial space readiness of various methods. These judgments must be made in the context of business models that address such questions as R&D costs, initial system capitalization, concepts of operation, anchor tenancy agreements, etc. A number of U.S. private initiatives as well as non-U.S. “public-private” initiatives are expected to come to fruition in the next 5-7 years. The generic types of such missions, their challenges, and their opportunities are discussed.

INTRODUCTION

It is no coincidence that The Land Remote Sensing Policy Act of 1992 (the Policy Act) was debated and adopted just as the Cold War was ending (Baker, O’Connell and Williamson, 2001). While no one seriously questions the value of remote sensing from the vantage point of space (Mondello, Hepner and Williamson, 2004a), sustaining a commitment to the continuity and advancement of such measurements – whether for civil, national security or commercial purposes – is far from simple or is the outcome guaranteed. Although initiatives to “privatize” Landsat go back as far as President Carter’s Presidential Decision Directive 54 in 1979, it is fair to conclude that there was no “commercial” remote sensing space industry until the initiatives of the early 1990’s that led to Title II of the Policy Act (Dehqanzada and Florini, 2000). Under President Clinton’s Presidential Decision Directive 23, and more recently under President Bush’s National Security Presidential Directive 27, it can be said that the U.S. now provides three programmatic pillars to its spaceborne remote sensing architecture: (1) civil; (2) national (including homeland) security; and (3) commercial. Some — but obviously not all — of the “bright-line” separations between these categories have been blurred, similar to the situation that has occurred in satellite weather systems with the convergence of the NOAA POES and Air Force DMSP programs into NPOESS. Thus the question: “What role do future U.S. commercial remote sensing systems play in the global matrix of land remote sensing satellite systems?”

* Work performed for NOAA/NESDIS Office of International and Interagency Affairs under Contract 50-SPNA-0- 00012.

Pecora 16 “Global Priorities in Land Remote Sensing” October 23 - 27, 2005 * Sioux Falls, South Dakota SPACE-BASED COMMERCIAL REMOTE SENSING VIABILITY

Any attempt to address the economic viability of space-based commercial remote sensing (CRS) is necessarily complex, particularly in the United States. The U.S. has a stated policy (OMB Circular A-76 [rev]*) that the government does not compete against the commercial interests of its citizens. With regard to operational weather satellites, the Policy Act forbids commercialization, including transfer to the private sector (privatization), thereby making such a conflict moot. However, that type of constraint was not placed on the Landsat program (Title I of the Policy Act) or any other “land remote sensing” program. This question of government competition does not arise in the majority of space-faring nations where “public-private partnerships” are the rule, rather than the exception. Given the large capital outlays necessary before any land remote sensing data can be produced from a spaceborne platform, questions of explicit or implicit government competition are highly relevant in the United States. Indeed, the raising of capital and the structure of a corporate business plan are as important as the specific technologies involved in producing commercial remote sensing data from space. Agencies of the U.S. Government do play a number of roles crucial to the success of the U.S. commercial remote sensing space industry besides acting as its regulators and implicit competitors (i.e., as the result of civil programs and technology demonstrations that release data at the cost of reproduction and distribution): (1) they act as major customers for commercial data, products and services; (2) they continue to play the dominant role in supporting the nation’s space industrial base; (3) they manage a great deal of the country’s space-related R&D funding; and (4) by sponsoring technology demonstration programs, USG agency programs yield datasets that can be used to test the potential for future commercial activity. In short, the public-private relationship in the U.S. is highly symbiotic, even if it is not an explicit partnership. Managing that relationship is critical to the future of commercial remote sensing from space in the U.S.

Determining Economic Viability

Since we are examining the future of commercial remote sensing from space, a brief examination of the commercial viability of other space activities is worthwhile. The most obvious examples are the following:

• Satellite Communications • Direct Broadcast Services • Positioning, Navigation and Timing • Weather Prediction

While the commercial space community may seem to be pursuing heuristic approaches to finding its holy grail of a “killer application” for satellite-based remote sensing, the underlying forces are rather more grounded in understandable economic theory:

• Does the method create valuable information; merely relay that information; or both? • Does the enterprise serve its users in parallel or in series, and what are the marginal costs of increasing the user base? • Does an end-user community already exist and, if so, is the goal of the new enterprise to provide those users with better value-for-money? • Who supplies the initial investment capital (i.e., before there is a revenue stream)? • Are there competitors for this market niche?

With respect to remote sensing from space, there is an established government user community in the U.S. and elsewhere, plus a slowly emerging commercial customer base. Commercial space providers face explicit competition from commercial aerial systems and — as noted above — implicit competition from U.S. and foreign civil, dual-use and/or technology demonstration programs. There are many technology risks associated with imaging the Earth from space, and those risks are magnified by the relative immaturity of certain advanced sensing methods. In short, the situation is rightly treated with caution by private equity capital. Without prejudging the

* Circular OMB A-76 (revised, May 2003), Subject: Performance of Commercial Activities, http://www.whitehouse.gov/circulars/a076/a76_incl_tech_corrections.pdf.

Pecora 16 “Global Priorities in Land Remote Sensing” October 23 - 27, 2005 * Sioux Falls, South Dakota eventual outcome of the present U.S. commercialization “experiment”, it is obvious that the USG must remain heavily involved in the U.S. CRS industry for the foreseeable future. By way of comparison, the GPS positioning, navigation and timing (PNT) system affords value-added providers with the compelling advantage of government development and operation of the space constellation. It serves all users in a fully parallel and simultaneous fashion. Moreover there is no system barrier to extension of the terrestrial user base (an unlimited number of receivers can be added in parallel). For this space-enabled service, the USG is and will remain heavily involved. Even the developers of analogous PNT satellite constellations generally speak of “augmentation of”, rather than competition with, GPS.

AN OVERVIEW OF REMOTE SENSING METHODS

While we recognize a rich variety of remote sensing techniques in Table 1, we must be reminded that commercialization of satellite remote sensing data has, to date, been limited to panchromatic (PAN), multispectral (MS) and Synthetic Aperture Radar (SAR) imagery. It is reasonable to assume that a successful commercial land remote sensor must be an imager, i.e., that there is an inherent spatial resolution associated with the data.

Table 1. Brief Description of Candidate Remote Sensing Methods

Method Passive Reflective or # of Bands Imaging or Spectral Region or Active Emissive Non-imaging Panchromatic P R 1 I 0.45-0.90 m (PAN) Multispectral P R I/NI 0.40-1.0 m 4-8 (MS) P R I/NI 1.0-2.5 P R/E 1-2 I/NI 3.0-5.0 P E 1-2 I/NI 10-12.5 Superspectral P R I/NI 0.40-1.0 m 8-20 (SS) P R I/NI 1.0-2.5 P R/E 3-5 I/NI 3.0-5.0 P E 3-5 I/NI 10.0-12.5 Hyperspectral P R 50-100 I/NI 0.40-1.0 m (HS) P R 100-300 1.0-2.5 P R/E ~250 3.0-5.0 P E ~250 8.5-11.0 Thermal IR P E 1 I/NI 8.0-12.5 m (TIR) Microwave (MW) P/A E/R 1 I/NI 0.2 – 1 mm Synthetic Aperture A R 1 I P, L, S, C, X, Ku Radar (SAR) LIDAR A R 2 I 0.5 – 11 m LADAR A R 1 I/NI 0.35 – 2 m

For PAN/MS imagery, U.S. commercial providers have moved to moderately high spatial resolution owing to real or perceived factors associated with the needs and policies of the U.S. and foreign governments. On the one hand, the CRS providers want to avoid competition with government-subsidized data from low-spatial-resolution civil systems. At the same time, governments have professed an interest in purchasing moderately high spatial resolution data, albeit within limits, for use in support of national security, foreign policy, and disaster response. Spatial resolution is not the only performance metric possessing commercial value. Spectral resolution, spectral region, polarization diversity, use of active versus passive techniques, use of methods that can better quantify reflectance properties (i.e., Bidirectional Reflectance Distribution Function [BRDF] measurements), and sensing of emissive versus reflective properties of terrestrial scenes provide unique information sources that may prove to have significant commercial, as well as scientific, value over the long run.

Pecora 16 “Global Priorities in Land Remote Sensing” October 23 - 27, 2005 * Sioux Falls, South Dakota How Can the Commercially Viable Space-Based CRS Methods Be Identified?

Overview. It is important to stress the distinction between the desirability of having particular satellite land remote sensing data sources and the probability that such systems will be commercially viable in this decade. In the electro-optic region of the spectrum, a 3-5 band MS imager co-registered with a higher resolution PAN imager represents the current commercial “baseline” system; a number of such imagery data sources having PAN resolution between 0.5-m and 3.0-m GSD are now, or may soon become, commercially available. It is difficult to predict which, if any, of these commercial providers will remain viable over the long run. One might easily conclude that the governments of the U.S. and France – the earliest providers of “widely disseminated” PAN/MS remote sensing data from space – are losing enthusiasm for acquiring and managing the costly assets necessary to obtain scientifically rigorous, lower resolution (ca. 5-30 meter) imagery characterized by a high areal coverage rate. Other countries will either pick up any slack in these traditional civil arenas or commercial entities may emerge as niche providers. Either way, the scientific continuity of such data may be at risk. National space agencies have been putting significant resources into higher spectral resolution and more intensive exploration of utility outside the VNIR region of the spectrum. This includes superspectral (SS) and hyperspectral (HS) imagery in the VNIR/SWIR, as well as imagery in the thermal IR (TIR) regions. There are niche commercial opportunities in this arena — previously realized by OrbImage with its OrbView-2/SeaWiFS MS/SS imager — if the initial capital investment required of the private provider is acceptable. Moving to active remote sensing methods, the field of commercial/civil/dual-use spaceborne SAR has become highly competitive among foreign nations; in the face of this competition, it is unlikely that a U.S. commercial remote sensing venture can succeed, absent a unique relationship with one or more U.S. Government agencies as an anchor tenant. Cost and technological risk appear to limit space-based LIDAR/LADAR payloads to the civil and/or technology demonstration arena for the rest of this decade. The current services being provided by commercial aerial LIDAR providers may help build a user community over the long run, but in the short run, these providers represent formidable competition to commercial space activity. There is an excellent reference for understanding the basic technology of worldwide civil, commercial, and technology demonstration space and aerial remote sensing systems (Kramer, 2002). Material on the majority of sensors cited in this paper can be found in Kramer’s excellent monograph. Panchromatic Imaging Systems. Moderate resolution panchromatic imaging systems can be expensive, but do not have to be so until their resolution becomes better than 1-2 meters. There is no unique cost model, however the general parameters that influence cost have been discussed (see, for example, Canavan, Thompson and Bekey, 1995). Models predict that the volume/cost of the sensor payload can scale as the cube of its telescope aperture (i.e., D3). The resolving power (i.e., the ground-resolved distance using the Rayleigh criterion) of a space telescope (Fiete, 1999) is given by GRD = 1.22 x (H/D). In the VNIR  0.65 m) for a LEO satellite orbiting at H = 450 km, the GRD is approximately 1.2 meters for a telescope aperture of D = 30 cm. This hypothetical example most closely approximates the early EROS imagers designed by Israeli industry for ImageSat International (ISI), although in the case of EROS-A, “oversampling” methods had to be used in order to approach its theoretical GRD value. The only currently operating commercial Pan imagers achieving better than 1-m GRD without oversampling (IKONOS and QuickBird) have telescope apertures a factor of 2 or greater than EROS-A. As noted above, that resolution improvement comes with a significant increase in cost associated with telescope aperture, payload volume and platform weight. While we estimate that there could be as many as a dozen civil, commercial and dual-use remote sensing systems with spatial resolution of 3 meters or better operating by the end of 2005, the vast majority will have a resolution coarser than 1 meter. To date, U.S. CRS providers have emphasized the combination of high spatial resolution, high areal coverage rate, and a high level of pointing agility and geolocational accuracy. This mix of metrics correlates strongly with high system — and imagery — cost; as a result, the majority of the U.S. CRS customer base for PAN imagery has been governments — U.S. and foreign. Two foreign initiatives in stereoscopic panchromatic imaging for mapping, charting and geodesy (MC&G) are noteworthy: (1) the two 10-m resolution HRS cameras on the French-led SPOT-5 platform; and (2) the two 2.5-m resolution cameras on India’s Cartosat-1 (scheduled to improve to 1-m resolution on Cartosat-2). Multispectral Imaging Systems. Until recently, multispectral imagery acquired from space platforms has been associated with Landsat (since 1972) and SPOT (since 1986). Although using different scan mechanisms and a somewhat different choice of spectral bands, each strived for large areal coverage rates and highly accurate radiometric calibration. Notwithstanding the remarkable data quality obtained from Landsat-7 and SPOT-5, other paradigms — including commercial ones — for acquiring MSI have been brought forward in the U.S. and abroad. Despite a recently announced plan for providing Landsat continuity on NPOESS, it may be that no single nation

Pecora 16 “Global Priorities in Land Remote Sensing” October 23 - 27, 2005 * Sioux Falls, South Dakota wishes to guarantee long term scientific data continuity of this type owing to its very considerable costs. Indeed the French government has announced that SPOT-5 is the last payload in this series. A solution to this scientific conundrum may arise out of the GEOSS program, either by tasking complementary civil systems from many nations or by developing an international cooperative venture. From a commercial vantage point, there may be advantages associated with straying from the strictures of Landsat/SPOT data continuity. Constellations composed of simpler, less expensive satellites, have received a great deal of attention, including the U.S. Resource 21 program (now cancelled), the German RapidEye program, and the Surrey Satellite Technology Laboratories DMC constellation and its VISTA constellation concept. The first two were conceived as commercial/dual-use programs and the latter two can be viewed as international data cooperatives. Superspectral Imaging Systems. As noted previously, many moderate spatial resolution technology demonstration and scientific satellites have increased the number of spectral bands to a level that deserves the appellation “superspectral” imagers (SSI). A range of spatial resolutions and swath widths are currently in operation. One could argue that OrbView-2’s SeaWiFS (8-bands) with 1 km best resolution was in fact the first commercial SSI, as well as the first NOAA-licensed CRS satellite flown successfully. Most of the well-known superspectral sensors flown to date — GLI, ASTER, MODIS, MTI, etc. — are not designed to provide operational land remote sensing data in the same manner as Landsat. Such R&D systems have more leeway to incorporate current technology in data storage and transmission, thus allowing more spectral channels and greater digitization depth to be employed. If an operational superspectral imager can be designed with only one or several main applications in mind (such as ocean color measurement), optical beam splitters and filters are still a viable — and cost effective — technical approach. It appears that moderate spatial resolution SSI payloads present a low-risk opportunity for a number of government and commercial applications covering the entire electro-optic region from the VNIR to the LWIR. There are examples of cooperative instrument development between the U.S. Government and U.S. industry (e.g., MODIS or MTI). The biggest hurdle may well be the potential for the U.S. Government competing with private industry as a data provider based on the nondiscriminatory data distribution provision of the Policy Act (re civil systems funded by the USG). Hyperspectral Imaging Systems. One of the attractions of hyperspectral imaging systems (i.e., imaging spectrometers) is their flexibility once deployed on-orbit. Because the spectral channels are sufficiently narrow to fully resolve any terrestrial scene, each new problem can be addressed by selecting a sub-set of the many (in some cases hundreds) available bands. HSI analysis is inherently machine based and non-literal. This means that value- added providers are likely to be an essential interface between the data producers and their commercial, or even their government, end-users. By contrast, government customers often wish to purchase only “raw” panchromatic and multispectral data together with the metadata needed to perform their own analysis of the imagery. The transition from beamsplitters and filters to imaging spectrometers is a large technological step. Hyperspectral imaging from space imposes severe constraints. The photons entering the primary aperture are now divided into a much larger number of spectral bins. At the same time, absolute radiometric calibration and high signal-to-noise ratios are even more important to accurate analysis than is the case with PAN, MSI or even SSI sensors. Direct comparison of established aerial HSI collections with spaceborne instruments as they are deployed represents a crucial element in validating the long-range prospects of commercial imaging from space (Kruse, Boardman and Huntington, 2003). Only one attempt to launch a commercial/dual-use hyperspectral imager has been made (the Warfighter-1 [WF-1] instrument on OrbView-4), unfortunately ending in a launch failure. Although several HSI instruments have been successfully flown, in every case to date, government agencies have played a major role in underwriting the development of the HS instrument. Like the AFRL sponsorship for the development of WF-1 instrument, future NOAA licensed providers may well require a “kick-start” for development of a commercial hyperspectral imager. Thermal Infrared (MWIR/LWIR) Systems. The terrestrial uses of broadband thermal IR (TIR) imaging have grown rapidly in the last decade. Technical advances have greatly increased the viability of moderate spatial resolution thermal imaging systems in space. While the economic benefits of applications such as early fire spotting would be enormous, so too might be the cost of producing an effective architecture (individual satellites and constellation) given that rapid response requires rapid revisit times. Europe has shown a great deal of interest in such systems (e.g., the German BIRD satellite and the Spanish FUEGO concept). The U.S. has pursued civil applications of DSP data, as well as using spectrally resolved TIR data from the Multispectral Thermal Imager [MTI] (Rodger, Balick and Clodius, 2005). Unlike many other remote sensing technologies, TIR imagery from space presents very obvious commercial and civil applications with high economic leverage.

Pecora 16 “Global Priorities in Land Remote Sensing” October 23 - 27, 2005 * Sioux Falls, South Dakota Synthetic Aperture Radar (SAR) Systems. In the last decade, enthusiasm for spaceborne SAR has grown rapidly in other countries. Canada has now operated the “multi-use” C-band Radarsat-1 for 10 years and hopes to launch Radarsat-2 — possessing a 3-m resolution Spotlight mode — within the next year or so. In addition to Canada’s capability in C-band, Germany (TerraSAR-X) and Italy (COSMO/SkyMed) anticipate offering commercial X-band SAR data taken from space at ground resolutions of approximately 1 meter. ESA continues to operate lower resolution civil SAR systems (e.g., ENVISAT/ASAR) and should soon be joined by others, notably Japan’s PALSAR system when that country launches its ALOS satellite. While SAR has been licensed by NOAA under the Policy Act, no U.S. firm has proceeded to develop a commercial spaceborne SAR system. NASA has been a world leader in developing SAR imagery systems, however the majority of that effort — including notable international partnerships — has employed the Space Shuttle as a platform for short duration missions such as the Shuttle Radar Topography Mission (SRTM) in 2000. NASA’s abandoned LightSAR initiative sought to include commercial partners in a civil/commercial dual-use satellite program. Such civil initiatives, as well as U.S. DoD “space radar” program, may well have confused the commercial landscape for SAR in the U.S. In short, any potential U.S. commercial space SAR provider — at least in C- or X-band — is fated to be “late to market” with respect to a number of foreign competitors. In addition, aerial SAR providers continue to be a significant competitive force. LIDAR and LADAR Systems. We are unaware of any plans to license a commercial spaceborne LIDAR/LADAR system. There have been over a dozen civil space LIDAR missions and one of the most ambitious, the NASA/CNES Cloud-Aerosol Lidar and Infrared Pathfinder Spaceborne Observations (CALIPSO) is schedule for launch together with CloudSat in Fall 2005. Huge advances in solid state laser technology applicable to building spaceborne LIDAR have been made in the last decade as the result of the massive investment in fiber-optic communications. While increased laser power is clearly important, recent improvements in electrical (i.e., wall-plug) efficiency are perhaps more so, since that high efficiency mitigates thermal management issues on the spacecraft. Despite this progress, spaceborne LIDAR incorporates a large number of high-risk and costly technologies. A recent discussion of the hurdles in moving from Low Earth Orbit (LEO) to higher orbits illustrates the nature of the difficulties confronting spaceborne LIDAR (Spiers, 2004b). Airborne LIDAR/LADAR systems have been proliferating over the last decade, and they have carved out a commercial niche by developing an extremely high spatial resolution 3-D mapping capability that cannot be duplicated from space. While spaceborne LIDAR is likely to provide critical civil and scientific data throughout this decade, the prospects for a commercially viable space- based system in this period are very poor.

SUMMARY AND CONCLUSIONS

Commercial PAN imagery from space has value beyond producing high quality Earth “photos”. Stereo imagers on a platform can produce DTED for use in Digital Terrain Models. Obviously, single imagers can so as well if the line-of-sight is scanned, typically through platform rotation. PAN imagery can be used to sharpen multispectral imagery taken in the same general wavelength region and can provide context for HS, SAR, TIR and other imagery data types that benefit from visual orientation. Finding the optimal spatial resolution for commercial systems (optimizing value-for-money) is a challenge; reducing system and operating costs is as important as increasing capability. The U.S. and the French-led SPOT consortium have dominated multispectral imagery from space in the past, but there are a number of viable competitors at present. Some of them, particularly India with the Oceansat, Resourcesat and Cartosat programs, are quite determined to field sizable and diverse constellations of operational satellites. Many organizations speak of the desire to commercialize hyperspectral imagery, but progress in that direction has been slow. In this arena, we expect that past is prologue; it is very likely that in the U.S. — as abroad — a government agency will actively participate in the development of any hyperspectral instrument that is flown under a NOAA commercial license. Many users would welcome a serious operational program to fly a commercial/dual-use TIR payload with capability different from Band 6 of Landsat; it would most likely be a small constellation of satellites hosting TIR payloads co-manifested with other sensor types. Such a capability would draw from significant strengths in the U.S. space industrial base.

Pecora 16 “Global Priorities in Land Remote Sensing” October 23 - 27, 2005 * Sioux Falls, South Dakota In the short run SAR opportunities for U.S. commercial providers, particularly in X-band or C-band, appear to have been pre-empted by other nations. Commercial applications for an L-band system may coincide with NASA interests if an appropriate public-private arrangement can be reached. LIDAR programs – aerial and civil spaceborne - have made remarkable strides, but the risk appears to be excessive for the U.S. commercial space industry at this time. In summary, we believe “advanced” commercial remote sensor initiatives will require government incubation/partnership programs as risk and cost reduction strategies. From our current vantage point, it is hard to envision “government-free” commercial viability. Government must continue to be involved as a customer for those data types that are best provided by privately operated remote sensing space systems. The predictability and stability of U.S. Government data requirements are vitally important to the commercial industry. Minimizing USG involvement in the operation of a U.S. private system once it is licensed for commercial operation is also crucial. The above challenges are representative, but by no means all inclusive; creating the long-term, sustainable partnership between the USG and U.S. industry mandated by NSPD-27 is very much a work in progress.

REFERENCES

Baker, J.C., O’Connell, K.M., and Williamson, R. A. [ed.] (2001). Commercial Observation Satellites: At the Leading Edge of Global Transparency. RAND Corporation and ASPRS Press, p. 5. Canavan, G., Thompson, D. and Bekey, I. (1995). Distributed Space Systems. In: New World Vistas: Air and Space Power for the 21st Century. Space Applications Volume, Chapter 5.5, pp. 123-145. Dehqanzada, Y.A. and Florini, A.M. (2000). Secrets for Sale: How Commercial Satellite Imagery Will Change the World. Carnegie Endowment for International Peace, Washington, D.C., pp. 40-45. Fiete, R.D. (1999). Image quality and FN/p for remote sensing systems. Optical Engineering, 38(7): 1229-1240. Kramer, H.J. (2002). Observation of the Earth and Its Environment: Survey of Missions and Sensors, 4th Edition. Springer-Verlag, Berlin Heidelberg New York. Modello, C., Hepner, G.F., and Williamson, R.A. (2004a). 10-Year Industry Forecast: Phases I-III – Study Documentation. Photogrammetric Engineering & Remote Sensing, 70(1): 7-58. Rodger, A.P., Balick, L.K., and Clodius, W.B. (2005), The Performance of the Multispectral Thermal Imager (MTI) Surface Temperature Retrieval Algorithm at Three Sites. IEEE Transactions on Geoscience and Remote Sensing, 43(3): 658-665. Spiers, G.D. (2004b). The challenge of active optical sensing from extreme orbits. In: Enabling Sensor and Platform Technologies for Spaceborne Remote Sensing (edited by G.J. Komar, J. Wang, and T. Kimura). Proceedings of SPIE Vol. 5659, Bellingham, WA, pp. 204-212.

Pecora 16 “Global Priorities in Land Remote Sensing” October 23 - 27, 2005 * Sioux Falls, South Dakota