WASHINGTON — Routine preparatory work on NASA’s Landsat Data Continuity Mission (LDCM) satellite has resumed following a pair of technical glitches earlier this year that added another three weeks of delay to the Earth mapping mission, agency officials said.
“Observatory testing has returned to the nominal flow and the schedule supports the current launch readiness date of Feb. 11, 2013,” said Ken Schwer, LDCM project manager at NASA’s Goddard Space Flight Center in Greenbelt, Md. As recently as mid-May, LDCM managers said they were working toward a launch readiness date of Jan. 23.
The LDCM spacecraft platform, provided by Orbital Sciences Corp. of Dulles, Va., will carry two main instruments: a $188 million medium-resolution camera called the Operational Land Imager, built by Ball Aerospace & Technologies Corp. of Boulder, Colo., and the $160 million Goddard-built Thermal Infrared Sensor (TIRS). The latter instrument was added to the spacecraft more than a year into the project.
Schwer said in an email July 26 that a “power short anomaly” damaged three electronics boxes on the LDCM spacecraft during an April test. These boxes were subsequently removed from the satellite and “have since been repaired and re-tested and re-integrated to the observatory and validated again.”
The other hiccup was a fill-tube leak on the TIRS instrument’s cryogenic cooler, Schwer said. Ball Aerospace built the cooler, which NASA officials believe may have sprung a leak when TIRS was shipped to Orbital’s Gilbert, Ariz., facility in January to be mated with the spacecraft.
The leak required engineers to add a valve assembly to the tube and repeatedly flush the cooler with liquid helium to remove any impurities that might have crept in. Following the fill-and-flush, the TIRS instrument “was turned on and checked out on Wednesday, July 25,” said Roz Brown, a spokeswoman for Ball Aerospace.
“Because of those issues, we’re a little bit behind where we would like to be,” Goddard Director Christopher Scolese said in a July 26 interview. “What we’re trying to do is to launch LDCM as soon as possible to minimize the probability that there will be a gap in the data set. Landsat 7 is working okay so we’re not in any imminent danger of a gap.”
The LDCM was selected to continue the 40-year-old Landsat program following the collapse of schemes to commercialize the mission or consolidate it aboard weather satellites. It is expected to cost $931.2 million to build, launch and operate for five years, according to a Government Accountability Office estimate published in March.
Landsat 7 and Landsat 5 are still operating, but only Landsat 7, launched in 1999, is collecting data from its primary instrument, the Enhanced Thematic Mapper Plus. Those data are degraded by a sensor glitch. Landsat 5, which launched in 1984, stopped transmitting Thematic Mapper imagery in November. The older satellite is still bringing in limited data from a backup sensor that recently was activated for the first time in longer than a decade.
LDCM will ride to space aboard a United Launch Alliance Atlas 5 rocket from Vandenberg Air Force Base, Calif. The satellite is in line at that range behind a NASA science mission called the Interface Region Imaging Spectrograph, which is scheduled to launch in late January.
Once LDCM is operational, about 400 images per day will be processed and delivered to users within 48 hours of collection via the Internet, said Jon Campbell, a spokesman for the U.S. Geological Survey, part of the U.S. Department of the Interior. The Geological Survey is responsible for distributing and archiving Landsat data.
“In practice we expect to exceed this requirement, but this leaves us sufficient margin in the event of problems at the Alaska or Svalbard, Norway, ground stations or disruptions in network service,” Campbell said. “We expect to make most data available as orthorectified products within 24 hours, which should satisfy most near real-time needs.”
Researchers, meanwhile, will be allowed to use a supercomputing facility called the NASA Earth Exchange to process Landsat imagery. Developed and hosted by NASA’s Ames Research Center at Moffett Field, Calif., the facility will allow researchers to “explore large Earth science data sets in hours, rather than months,” Waleed Abdalati, NASA’s chief scientist, said July 23 at a joint NASA/Interior Department press conference.
With the Ames-developed supercomputer, “scientists can put Landsat image tiles together like a giant jigsaw puzzle,” creating maps comprising more than half a trillion pixels in fewer than 10 hours, Abdalati said.
