Landsat Data Gap Background

The Landsat suite of satellites has collected the longest continuous archive of multi-spectral data of any land-observing space program. From the Landsat program’s inception in 1972 to the present, the Earth science user community has benefited from a historical record of remotely sensed data. The archive of Landsat data constitutes the longest continuous record of satellite-based observations and, as such, is an invaluable resource for monitoring global change and the use of Earth observations in decision making tools that benefit society. In order to meet observation requirements at a scale revealing both natural and man-induced changes on the landscape, the Landsat program provides the only 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. The Landsat 5 (L5) Thematic Mapper (TM) sensor was launched on March 1, 1984. It has been on-orbit for more than 22 years and has continued to perform well over a period of time far exceeding its design life of three years. Nevertheless, the instrument has aged and its characteristics have changed since launch. Currently, L5 TM has no capability to record and re-broadcast acquisitions; its duty cycle has been reduced and it could systematically fail at any time.

The Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) sensor was launched on April 15, 1999 with a design life of five years. It has been on-orbit for more than seven years. Landsat 7 has suffered from a Scan Line Corrector (SLC) malfunction starting on May 31, 2003, and is marginally capable of acquiring global coverage in a timely manner. It is likely that either or both the Landsat 7 and Landsat 5 satellites could fail completely after several more years of curtailed operations and both satellites will likely run out of fuel before the end of 2010. The Earth observation community is facing a probable gap in Landsat data continuity before Landsat Data Continuity Mission (LDCM) data arrive in approximately 2011. A data gap will interrupt a 34+ year time series of land observations.

Other than the anticipated LDCM, 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 Land sat 7 fail before the launch of LDCM, there will be no direct replacement available for the Landsat 7 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.

Landsat Data Gap Study Team

The federal agencies responsible for Landsat Program Management, NASA and DOI USGS recognized the possibility of a Landsat data gap and convened a Study Team beginning in early 2005. The Study Team recognized that no current or near-future satellite system could fully replace the Landsat satellites but concluded that the capture and archival of data from comparable systems could reduce the impact of a data gap. The Study Team assessed the characteristics of multiple systems and identified sensors aboard India’s ResourceSat satellite and sensors aboard the China Brazil Earth Resources Satellite (CBERS) as the most promising sources of Landsat-like data. The Study Team also concluded that 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 Center for Earth Resource Observations and Science (EROS), 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

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

Documents

This page lists documents directly related to the Landsat Data Gap Studies.

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 (15.0 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 (2.31 MB)

CBERS-2

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