Engineers at Goddard Space Flight Center inspect and move the Thermal Infrared Sensor (TIRS) after two months of testing in the thermal vacuum chamber. TIRS completed its first round of thermal vacuum testing on Tuesday, October 4, 2011. Credit: NASA
From the very beginning it was a looming ticking countdown clock to get the Thermal Infrared Sensor (TIRS) instrument ready for the Landsat Data Continuity Mission launch. Even on their very first day, the TIRS development team started a year behind schedule to design, build and test an instrument in three years instead of the more typical four-year development cycle.
The project began on a tight schedule, but then outside forces intervened. There was the earthquake, hurricane and a near government shut down-but that didn't stop the TIRS team from being ready for a successful Landsat launch on February 11. "We received our first image from the TIRS instrument on March 7, and it was just spectacular," said Betsy Forsbacka, TIRS instrument manager at NASA's Goddard Space Flight Center in Greenbelt, Md.
TIRS came about to help scientists and resource managers monitor water evaporation and transpiration over land surface by measuring radiation emitted in two thermal bands of the electromagnetic spectrum. TIRS operates at a resolution of 100 meters (328 feet), allowing for monitoring fields for agriculture, which is especially important for water managers. The instrument was a relatively late addition to the Landsat mission, which is why there was a tight production schedule.
"We took three years here at NASA Goddard to take it from initial concept development design, go through all the major reviews to make sure the design was valid, then build and test the instrument, which we did here at NASA Goddard," Forsbacka said. "We delivered the instrument to Orbital Sciences Corp., in Gilbert, Ariz., we integrated onto the spacecraft, and we tested the two instruments and the spacecraft as one large system. In December we delivered the spacecraft with instruments aboard to the launch site and launched on February 11 at Vandenberg Air Force Base in California."
› Larger image
Aleksandra Bogunovic reaches across the instrument to affix the corners of a Multi-Layer Insulation blanket to the TIRS instrument. In January 2012, TIRS was shipped to Orbital Science Corp. in Gilbert Ariz. where it was integrated onto the LDCM spacecraft. Credit: NASA
As the TIRS deputy instrument manager and now instrument manager, the largest unyielding aspect of the project Forsbacka had to manage was time. "For us, it was schedule, schedule, schedule," he said. "Time was the one thing we couldn't make. If we didn't make our delivery date, we would not fly." And then there were the events that couldn't be anticipated. Even with tight project management planning, who could have foreseen an earthquake and hurricane occurring within one week, but that is what happened in August 2011.
The team was in the midst of thermal vacuum testing, cycling between very hot and very cold temperatures, when the earthquake tremors began. The test team fled the building, and when it was safe to return, the instrument was put into a safe configuration. A couple of days of testing were lost while the team determined if there was any damage. "Actually launch is harsher than the earthquake," Forsbacka commented, "but you don't know that at the time and you wonder what is happening to the instrument."
Just on the heels of the earthquake, time was lost to planning for Hurricane Irene, which was forecast to arrive only days after the earthquake. The hurricane diverted the schedule by a couple of days for planning essential personnel in the event of a NASA Goddard campus closure and determining what testing would take place and which tests would be put on hold in the event of a severe hurricane. It turns out there was even more unplanned excitement to come for the TIRS team.
Because TIRS uses Quantum Well Infrared Photodetectors (QWIPs) to detect specific light wavelengths used to measure surface temperature, TIRS had to be outfitted with a cryocooler to keep the QWIP detectors working at the necessary cold temperatures. The cryocooler supplied by Ball Aerospace-the project's largest procurement-was also being developed on a compressed timetable. To keep TIRS on schedule, members of the NASA Goddard TIRS team worked onsite at the Ball Aerospace facility in Boulder, Colo., for a year to facilitate swift decisions.
"After going through all of the steps of this very complicated procurement, and the design, build, and all the reviews, and getting it through environmental testing, when it came time to ship the cryocooler, it was the weekend of the potential government shutdown in April 2011 [due to a stalled spending deal in Congress]," Forsbacka said. "How do you plan for that?" So the TIRS team worked at a furious pace with Ball Aerospace to get the unit shipped to the NASA Goddard campus as quickly as possible.
But the TIRS team faced a host of uncertainties about being allowed to report to work due to moratoriums over weekend work. And the cryocooler was in transit to be delivered on a Friday, on the day of the pending shutdown. Forsbacka said the team had to weigh the options. "Do we delay it? With our schedule, we didn't delay anything if we could avoid it. We couldn't get it delivered earlier. If it arrived on time, would anyone be here to receive it?"
Simple variables such as the delivery truck being delayed due to getting stuck in traffic at various points from Boulder also had to be considered. As it turns out, the cryocooler arrived that Friday night, barely before the midnight cutoff, and just before the team was no longer allowed to work due to the imminent government shutdown.
Beyond the earthquake, hurricane and threat of a government shutdown, a host of decisions along the way kept the project on track for meeting the launch deadline. At the beginning during the TIRS design, the team focused on meeting requirements rather than seeking perfection. In some cases when a requirement was hard to meet, they asked the scientist if it was a number they absolutely had to have. "In some cases the answer was yes, but in many cases, what you have is good enough," Forsbacka said. "If you don't communicate with your scientists, you can chew up a lot of time."
Each requirement builds in a worst-case scenario, said Dennis Reuter, the TIRS instrument scientist who authorized any TIRS requirements changes. Sometimes if one requirement meets specifications, another one can be relaxed to still perform the desired task, he said.
Testing also helped keep TIRS development on track. "We tested much earlier and more often with TIRS than we normally do to meet the accelerated schedule," Reuter said. Instrument subsystems were also developed in parallel so one delay wouldn't hold up the schedule.
"Schedule is everything, and we couldn't afford to lose even a day," Forsbacka said. "Over three years, if you lose a day, it turns into a week, then a month and then you don't fly." She said it was particularly challenging to get all of the subsystems delivered so the instrument could be assembled for testing. "If there is one subsystem not delivered, it is a showstopper," she said.
The Landsat Program is a series of Earth-observing satellite missions jointly managed by NASA and the U.S. Geological Survey. Once LDCM completes its on-orbit check-out phase in late May, the satellite will be turned over to the USGS and renamed Landsat 8. Data from TIRS and the Operational Land Imager will be processed and added to the Landsat Data Archive at the Earth Resources Observation and Science Center in South Dakota, where it will be distributed for free over the Internet.
› Learn more about TIRS and its applications
› Landsat's TIRS Instrument Comes Out of First Round of Thermal Vacuum Testing
› NASA Landsat's Thermal Infrared Sensor Arrives at Orbital
› NASA Earth Observatory: Water Watchers
› Landsat mission
› USGS's Landsat mission page