Long-overdue Landsat Will Put Ground System to the Test
SAN FRANCISCO — When the U.S. Geological Survey (USGS) began providing free Landsat Earth imaging data to customers in 2008, program officials expected demand to swell before leveling off.
Instead, demand for Landsat scenes “continues to grow and continues to grow” as researchers and policymakers around the world find new applications for Landsat’s 40-year archive of moderate-resolution Earth imagery, said Jenn Sabers, Remote Sensing Branch chief at the USGS Earth Resources Observations and Science (EROS) Center near Sioux Falls, S.D.
Before the free-data policy was established, EROS sold approximately 53 Landsat images per day. Since then, demand for Landsat imagery has grown almost 100-fold, Sabers said. EROS currently supplies customers with roughly 5,000 daily scenes, said Jim Nelson, ground systems manager for the Landsat Data Continuity Mission (LDCM), which NASA plans to send into sun-synchronous orbit Feb. 11 on aAtlas 5 rocket from Vandenberg Air Force Base, Calif.
Once LDCM begins returning data, program officials anticipate another significant jump in demand for imagery due, in part, to the greater capability of the new satellite’s onboard instruments. Landsat 7, which was launched in 1999, employs its Enhanced Thematic Mapper Plus to produce 250 images per day. In contrast, LDCM, which will be renamed Landsat 8 once the spacecraft is in orbit, will carry two instruments to produce 400 daily images, Nelson said.
The LDCM spacecraft, built by Orbital Sciences Corp. of Dulles, Va., carries two instruments. The Operational Land Imager built by Ball Aerospace & Technologies Corp. of Boulder, Colo., is designed to obtain data in nine spectral bands. The Thermal Infrared Sensor built by NASA’s Goddard Space Flight Center in Greenbelt, Md., is designed to gather data in two additional spectral bands. The new instruments, like the overall LDCM mission, are designed to provide researchers with data that are consistent with previous Landsat missions while also taking advantage of technological advances to collect new types of remote sensing data, Sabers said.
The Operational Land Imager includes seven data channels similar to those of Landsat 7’s Enhanced Thematic Mapper Plus as well as two additional channels. One of the new channels is designed to obtain data in an ultrablue band, which is used to study water and atmospheric aerosols, while the second is designed to detect high-altitude cirrus clouds.
With LDCM, EROS is taking on an expanded role in the Landsat program. For Landsat 7, NASA was responsible for developing the spacecraft, instruments and ground systems in addition to overseeing satellite launches and initial flight operations, while USGS was charged with operating the orbiting satellites and handling data processing, distribution and archiving. For LDCM, USGS took the lead in developing and building the mission’s ground-based infrastructure. That division of labor played to each agency’s strengths, including USGS’s expertise in capturing land remote sensing data, processing that data and working with customers to provide data products suited to their needs, Sabers said.
“This is the first time EROS has had the opportunity to be involved at the start of the mission,” Nelson said. EROS worked closely with NASA and Landsat contractors to develop “the ground system in parallel with the space systems in order to ensure compatibility along the way.”
The result of that partnership is a space-to-ground communications system that will enable ground stations to support multiple Landsat missions with commodity hardware. Ground systems will no longer need to be developed to support specific missions, Nelson added.
The EROS team also redesigned the Landsat data processing and archiving system to meet the demands of existing and future data customers. For example, the LDCM ground system is designed to process all of the Landsat Earth imagery to provide an accurate depiction of terrain and make those scenes available to customers within 24 hours. Previous Landsat ground systems maintained raw data. Specific data sets were processed and distributed in response to customer requests.
In addition, EROS developed new Web-based products. “Data customers will be able to browse through full-resolution, JPEG images of the visible spectral bands to obtain a quick look at the imagery,” Nelson said.
USGS will manage LDCM flight operations in a mission operations center located at Goddard. LDCM ground stations are located in Fairbanks, Alaska; Svalbard, Norway; and Sioux Falls.
In preparation for the LDCM launch, USGS and NASA officials have conducted extensive testing of all elements of the ground-based infrastructure, including the mission operations center, the LDCM ground stations, data processing and archiving systems.
Once the satellite launches, NASA and USGS officials plan to spend approximately 90 days confirming that the satellite and instruments are operating properly. “We do not plan to distribute scientific quality data until the end of that period,” Nelson said. However, the LDCM team plans to make a few images publicly available as soon as officials are confident that the spacecraft and instruments are healthy, he added.
When EROS was established in 1973 as a receiving station for Landsat imagery, it had one mainframe computer and fewer than a dozen employees. Nearly 40 years later, 661 people work at EROS, including 148 government employees and 513 contractors, EROS spokeswoman Janice Nelson said.