Remote Sensing Technologies

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Landsat Data Gap Studies

Landsat Data Gap Background

The Landsat suite of satellites has collected the longest continuous archive of multispectral data of any land-observing space program. From the program’s inception in 1972 to the present, Landsat data has been a valuable resource for monitoring global change and the use of Earth observations in decision making tools benefiting society. In order to meet observation requirements at a scale revealing both natural and human-induced changes on the landscape, the Landsat program provides an inventory of the global land surface over time on a seasonal basis.

The Landsat program has surpassed three decades of imaging the Earth’s surface. Landsat 5 (L5), with the Thematic Mapper (TM) sensor, was launched on March 1, 1984, and continues to perform well past its design life of three years. Nevertheless, the instrument has aged and its characteristics have changed since launch. Currently, the TM sensor has no capability to record and re-broadcast acquisitions and its duty cycle has been reduced.

Landsat 7 (L7), with the Enhanced Thematic Mapper Plus (ETM+) sensor on board, was launched on April 15, 1999, with a design life of five years. Although a Scan Line Corrector (SLC) failure occurred on May 31, 2003, L7 is still acquiring global coverage in a timely manner. It is likely, and expected, that either or both satellites could systematically fail completely or run out of fuel before the launch of the Landsat Data Continuity Mission (LDCM), planned for mid-2011.

No other domestic or international satellite program, current or planned, has the onboard recording capacity, direct-downlink receiving station network, and archive/production systems to routinely perform the full Landsat mission. If Landsat 5 and Landsat 7 fail before the launch of LDCM, there will be no direct replacement available for the Landsat data stream entering the Department of the Interior’s (DOI) U.S. Geological Survey (USGS) National Satellite Land Remote Sensing Data Archive (NSLRSDA) in Sioux Falls, South Dakota. A data gap will interrupt a 35+ year time series of land observations.

Landsat Data Gap Study Team

Federal agencies responsible for Landsat Program Management, National Aeronautics and Space Administration (NASA), and DOI USGS recognized the possibility of a data gap and convened a Study Team beginning in early 2005. The team recognized that, although no current or near-future satellite system could fully replace the Landsat satellites, capturing and archiving data from comparable systems could reduce the impact of a data gap. The team assessed the characteristics of multiple systems and identified sensors aboard India’s ResourceSat satellite and the China Brazil Earth Resources Satellite (CBERS) as the most promising sources of Landsat-like data. More in-depth technical evaluations of the data and capabilities of these systems are required before mission gap mitigation strategies can be fully formulated. The findings of the Study Team were presented to representatives of Office of Science and Technology Policy (OSTP) and Office of Management and Budget (OMB) on June 15, 2005.

An interagency Data Characterization Working Group (DCWG) was formulated to coordinate and leverage expertise from the technical staffs at three field centers, the NASA Goddard Space Flight Center (GSFC), NASA Stennis Space Center (SSC), and the USGS Earth Resource Observations and Science (EROS) Center, along with several collaborating universities. The aim was to perform an initial data quality assessment of image products acquired from foreign systems having the potential to mitigate an expected Landsat Mission data gap.

Landsat Data Gap Requirements

The Landsat Data Gap Study Team defined a set of minimum data-acceptance criteria for these sources, which would most likely replace only a portion of the Landsat data stream during a pre-LDCM data gap.

Baseline Specifications

Performance Parameter Performance Goal: LDCM Specification Baseline Specification1
Spectral Bands2 Blue: 350-515 nm
Green: 525-600 nm
Red: 630-680 nm
NIR: 845-885 nm 3
SWIR(1): 1560-1660 nm
SWIR(2): 2100-2300 nm
Green: 525-600 nm
Red: 630-680 nm
NIR: 845-885 nm 2
SWIR(1): 1560-1660 nm
Radiometry <5% error in at-sensor radiance, linearly scaled to image data <15% error in at-sensor radiance, linearly scaled to image data
Spatial Resolution 30m GSD VNIR-SWIR; 15m panchromatic 10-100m GSD
Geographic Registration <65m circular error <65m circular error
Band-band registration uncertainty <4.5m (0.15 pixel) uncertainty <0.15 pixel
Geographic Coverage All land areas between ± 81.2º north and south latitudes, including islands, atolls, and continental shelf regions of less than 50m water depth All land areas between ± 81.2º north and south latitudes at least twice per year

1Acquired data must be characterized and verified against these specifications to ensure data quality and continuity.
2Landsat/LDCM bands given; show and discuss any differences from these nominal bandwidths.
3NIR bandwidth given for LDCM; Landsat bandwidth of 780-900 nm is also acceptable.

Documents

LDGST Overview

  • LANDSAT DATA GAP STUDY Technical Report – Initial Data Characterization, Science Utility and Mission Capability Evaluation of Candidate Landsat Mission Data Gap Sensors – PDF (9.86 MB)
  • Landsat Data Gap Study Team Activities Poster – PDF (33.6 MB)
  • Landsat Data Gap Studies: Potential Data Gap Sources – PDF (4.50 MB)

IRS-P6

  • Overview of the ResourceSat-1 (IRS-P6) – PDF (809 KB)
  • Cross-Calibration of the Landsat 7 ETM+ and Landsat 5 TM with the ResourceSat-1 (IRS-P6) AWiFS and LISS-III Sensors – PDF (373 KB)
  • Evaluation and Comparison of the IRS-P6 and the Landsat Sensors – PDF (3.82 MB)

CBERS-2

  • Cross-Calibration of the L5 TM and the CBERS-2 CCD sensor – PDF (1.15 MB)

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