Heliophysics missions move toward operations
NEW ORLEANS - Two NASA heliophysics missions launched together in September are performing well, while a third mission launched earlier this year is beginning limited operations despite problems with one spacecraft.
At the recent Annual Meeting of the American Geophysical Union, scientists released the first data from the Interstellar Mapping and Acceleration Probe (IMAP) and the Carruthers Geocorona Observatory. Both spacecraft launched aboard a Falcon 9 rocket in September along with NOAA's Space Weather Follow-On L1 satellite.
The spacecraft have yet to reach their destination, a halo orbit around the Earth-sun L1 Lagrange point about 1.5 million kilometers from Earth. Scientists, however, have been commissioning the instruments while the spacecraft are en route.
During a conference session on IMAP Dec. 15, David McComas, the mission's principal investigator at Princeton University, said that when abstracts were submitted for the meeting, the mission had not yet launched. IMAP carries 10 instruments to study the heliopause and measure the solar wind flowing from the sun.
"We weren't sure exactly when we would launch. We weren't sure how long it would take to commission the instruments," he said. "But I'm delighted to say that all 10 instruments are on."
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Those instruments are still being tuned, McComas said, but they are already collecting high-quality science data. "We're in a super great position."
Commissioning since launch has gone smoothly, said Nathan Schwadron, co-deputy principal investigator for IMAP at the University of New Hampshire, at a Dec. 16 briefing. "We're getting great data. It's beyond my imagination how smoothly this has gone," he said.
IMAP is scheduled to perform a maneuver in early January to insert itself into the halo orbit around L1. The mission's prime science phase is set to begin Feb. 1.
The accuracy of the launch allowed IMAP to conserve hydrazine propellant reserved for correction burns, extending its potential lifetime. The mission has a two-year prime science phase, said Eric Christian, another co-deputy principal investigator at NASA's Goddard Space Flight Center, at the briefing.
"There's fuel for much more than that," he said, noting the propellant is used to maintain the halo orbit. "We've got enough fuel for many, many years. As long as there is fuel and funding and things are working, we're going to try to still do science."
The Carruthers Geocorona Observatory is designed to study Earth's exosphere and its faint ultraviolet glow, known as the geocorona. At the AGU meeting, NASA released the first images of Earth and the moon taken by the spacecraft during its journey to L1, including views of the geocoronal glow surrounding Earth.
Carruthers is NASA's first mission dedicated to studying the geocorona, which was first observed in images from an instrument designed by the mission's namesake, George Carruthers, and deployed on the moon on an Apollo mission.
The geocoronal emission comes from hydrogen atoms created when water molecules break apart into hydrogen and oxygen and escape into space, the same process that caused Mars to lose its water, said Lara Waldrop, the mission's principal investigator at the University of Illinois, during a Dec. 16 briefing. The density of the exosphere also influences how quickly Earth's magnetosphere recovers from solar storms by dissipating excess energy.
In the first image from Carruthers, the geocorona filled the camera's field of view. By the time the spacecraft reaches L1, Waldrop said, it should be able to image the full geocorona for the first time. "We're really excited," she said.
While IMAP and Carruthers are performing well, another heliophysics mission launched earlier this year has encountered problems. The twin Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites, or TRACERS, launched into Earth orbit aboard a Falcon 9 rideshare mission in July. One spacecraft, SV2, functioned normally after launch, but controllers experienced difficulties maintaining communications with the other, SV1.
NASA said Dec. 12 that engineers determined the batteries on SV1 are not functioning, limiting operations to periods when the spacecraft is in sunlight. NASA said the two spacecraft are now making "limited, routine tandem measurement"s near the southern polar cusp of Earth's magnetic field, studying how the solar wind couples with the magnetosphere.
The mission was designed for the two spacecraft to pass through the same region of space up to two minutes apart to observe how conditions change over that time.
"Full assessment of the impacts to the mission's science goals continues as the mission team develops a new operational plan to commission the instruments on Space Vehicle 1 within the new mission constraints," NASA said in a statement.
In a presentation at the AGU meeting Dec. 15, David Miles, principal investigator for TRACERS at the University of Iowa, said he remains optimistic the mission can achieve its objectives despite the power limitations.
"It's currently running only on the dayside and with a reduced instrument payload," he said of SV1. "We are continuing to commission it, and we look forward to having a complete payload on both spacecraft."
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