The 50-year Landsat Program lies at the heart of the USGS Earth Resources Observation and Science (EROS) Center, so naturally there are a few Landsat elements on display. Well, more than a few—imagery lines the lengthy hallways, displays divulge Landsat’s details and a model of Landsat 8 hovers above the lobby.
USGS Satellite Sensor Finds Home with Smithsonian
However, one familiar artifact has left the illumination of EROS’ central atrium for a new home where it will be seen by vast numbers of visitors.
The Landsat 7 Enhanced Thematic Mapper Plus (ETM+) instrument, an engineering model of the instrument currently orbiting and imaging the Earth’s surface, had resided since the early 2000s in the area between EROS’ front desk and the rotating globe. On March 7, 2023, a crew of three contracted by the Smithsonian Institution hoisted its heft of hundreds of pounds carefully from its display platform with specially made hooks attached to chains on a pulley system suspended from a soaring metal frame on wheels. They walked the frame over to a crate bottom, lowered the ETM+ into place, secured its peg-type legs with wood, built the rest of the crate around it, strapped it in and wrapped the crate with plastic.
For Kris Piper, USGS Supervisory Property Manager at the EROS Center, which celebrates its 50th anniversary in 2023, the move is bittersweet. She has been helping plan the move for a couple of years and watched over the operation of getting the ETM+ out of the building and loaded into a truck for its trek to a spot all prepared in the Smithsonian National Air and Space Museum in Washington, D.C.
“I’m going to miss it being here. It’s part of our history, and now it’s leaving. It was always really neat to show people,” said Piper, who joined the EROS staff in 2005 and said the move is the culmination of an informal agreement among NASA, the USGS and the Smithsonian dating to 1999, the year of Landsat 7’s launch.
Piper takes consolation in the fact that millions of people may now see it each year, as well as “the excitement of it being at the Smithsonian, so when I go to the museum, I can see that and say, ‘That was here at EROS.’ ”
And because of the move, Smithsonian visitors will learn what Piper already knows—about Landsat 7’s past and future and how the entire Landsat Program continues helping people around the world after a half-century of Earth observations.
What exactly is the ETM+?
Landsat 7 launched April 15, 1999, to join in orbit Landsat 5, which had been collecting data alone since 1993 and in total since 1984. Landsat 7 contains the ETM+ sensor, which improved on the successful Thematic Mappers on Landsat 4 and 5.
New features on the ETM+ that benefited the continued monitoring of land cover and land change included an on-board data recorder; a high-resolution panchromatic band, whose imagery appears black and white; and a thermal infrared band with an increased resolution over the Thematic Mappers’ thermal band.
The ETM+ at EROS was a functioning sensor in the lab where the ETM+ currently in orbit was built, according to contractor Digital Data Team Lead Ron Hayes, who has worked at EROS since 1994 and was part of the Landsat 7 calibration team. He recalled that the engineering model originally was adapted from a bench test ETM sensor for Landsat 6, a satellite that failed to reach orbit upon launch in 1993. When no longer needed, the ETM+ went on display at EROS with all of the working components, except that Mylar replaced the scan mirror, Hayes said.
The Scan Line Corrector (SLC) inside the ETM+ on Landsat 7 failed on May 31, 2003, and it could no longer remove the typical “zigzag” motion caused by the combination of differing movements of the scan mirror in the ETM+ and the spacecraft itself advancing forward. From that point on, Landsat 7 scenes have gaps that represent the loss of more than 20% of the data. The instrument’s other components continue to operate at the same level of accuracy and precision, so image pixels are still accurately calibrated, and methods have been developed to fill the data gaps.
Model’s Use in an Emergency
Jim Lacasse, now Landsat Operations Project Manager at EROS, shifted departments at EROS and became the Mission Management Officer for Landsat 5 and 7 just months after the SLC failure.
“One of my first things was working on what to do because they were studying what happened, what the root cause was and if they could bring it back. So we were looking at what we could do with the products and what mitigation strategies we could have,” Lacasse said. Methods commonly used for Landsat products today were unheard of in 2003, including gap-fill products he looked at with NASA that, at the time, “were like heresy.”
Lacasse recalled that part of the investigation into the cause involved pulling the SLC out of EROS’ ETM+ engineering model and sending it to the manufacturer and NASA contractor in Santa Barbara, California, to experiment with since the cause seemed likely to be mechanical rather than electrical. A definite cause has not been determined.
Later, the SLC came back to EROS. “I had it sitting in my office here for years,” Lacasse said. More recently, it was sent to the Smithsonian to go on display and await the arrival of the ETM+ instrument.
Landsat 7’s Extra Missions
Landsat 8 joined Landsat 7 at an altitude of 438 miles in 2013, the year Landsat 5 was decommissioned. Landsat 8 contained instruments that improved on the ETM+ and had fewer moving parts: the Operational Land Imager and the Thermal Infrared Sensor. Landsat 9, similar to Landsat 8, launched in 2021, and Landsat 7 completed its science mission on April 6, 2022.
However, the Landsat 7 ETM+ is still hard at work, albeit in a slightly lower orbit. It resumed imaging May 5, 2022, for an extended science mission that is being monitored to ensure that the data is nominal. For the first time, three Landsat satellites are collecting data at the same time, which covers areas of the Earth’s surface more frequently.
Landsat 7 has yet another task in store after its extended science mission ends. In a first-of-its-kind attempt, NASA is preparing to robotically refuel Landsat 7, a satellite not designed to be serviced, to test the ability to extend the life of satellites in orbit. The On-orbit Servicing, Assembly and Manufacturing 1 mission (OSAM-1) is planned for launch around 2026.
Lacasse looks forward to the OSAM-1 mission, although he plans to retire before then. When OSAM-1 closes in on Landsat 7, he said, the operators will maneuver it around the satellite, which no one has laid eyes on in nearly 25 years. “They’ll have super high-resolution cameras that they’ll be able to take pictures of it,” he said. “I’d like to see that.”
A Work Highlight
While it represents a long effort for quite a few people at EROS, and especially Piper, she considers the ETM+ project a highlight of her property work.
“It was really fascinating watching how the crew members work and thinking that something we had here is going to the Smithsonian,” Piper said.
So, will visitors to EROS from now on just walk down a long empty stretch to get to the rotating globe from the lobby? Not if Piper has a say.
“I’ve got some ideas, thinking of what we can put in the sensor’s place there for tours. I think it’s important that we have something to replace it.”
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