NASA officials expressed joy over the weekend, saying the first of a pair of space probes is successfully orbiting the moon.
“Pop the bubbly & toast the moon! @NASA’s #GRAIL-A spacecraft is in lunar orbit,” the space agency posted on Twitter.
“With GRAIL-A in lunar orbit we are halfway home,” said David Lehman, GRAIL project manager at NASA’s Jet Propulsion Laboratory. “Tomorrow may be New Year’s everywhere else, but it’s another work day around the moon and here at JPL for the GRAIL team.”
The probe, the first of two, was eased into position on Saturday. The first Gravity Recovery and Interior Laboratory (GRAIL-A) began orbiting the Moon at about 2201 GMT, according to officials at NASA’s Jet Propulsion Laboratory in Pasadena, California.
Controllers at the NASA Jet Propulsion Laboratory erupted in cheers after receiving a signal that the probe is functioning and circling the moon. The team is expected to repeat the success on Sunday, moving an identical probe into position over the moon.
The announcement comes as NASA officials expressed confidence in their chances of successfully carrying out the mission to the moon. Speaking Monday, the team expressed confidence that the mission will continue to perform flawlessly, adding that they expect to gather an unprecedented amount of data from the mission.
“Both spacecraft have performed essentially flawlessly since launch, but one can never take anything for granted in this business,” said mission chief scientist Maria Zuber of the Massachusetts Institute of Technology.
Engineers said the chances of the probes overshooting are remote, noting that since their launch in September their trajectories have been precise. The U.S. space agency, which is facing serious budget cuts, said the pair of probes are taking 30 times longer than the Apollo space program to reach the moon. The team said they were relying on a low-energy, high-cruise time trajectory to reach the moon.
The low-energy, high-cruise time trajectory is beneficial for mission planners and controllers, as it allows more time for preparing the pair of spacecrafts, and NASA said the path would allow the program to save money and increase the chances of a successful mission.
The $496 million mission will measure the moon’s lumpy gravity field to gather data on Earth’s nearest neighbor.
The mission, which launched earlier this year in September, is thus far the largest bet for the space agency in recent years. This mission is, in some ways, a twin of the earlier NASA GRACE mission, which tracks geophysical, gravitational, and climate changes here on Earth. GRACE is able to determine groundwater sites, droughts, and also completed a detailed gravitational map of the Earth.
Speaking earlier this week, NASA scientists expressed confidence that the moon mission would remain on track.
“The anxiety level is heightened right now, and it is more so than with other missions, because we do have two spacecraft to go into lunar orbit,” Grail project manager David Lehman of JPL told reporters. “But we’ve been studying and working on this for three or four years — four years — and we’re well-prepared for that.”
Once in orbit, the pair of space probes will spend two months following each other around the moon. Scientists back on Earth will measure the varying distance between the pair of spaceships to calculate the lunar gravity field. NASA officials said the pair of probes are specifically tasked with measuring the uneven gravity field of the moon and determine what lies beneath — straight down to the core. Both GRAIL-A and GRAIL-B will reportedly spend upwards of 90 days gathering data to create the first complete high-resolution map of the Moon’s gravitational field.
When science collection begins, the spacecraft will transmit radio signals precisely defining the distance between them as they orbit the moon in formation. Regional gravitational differences on the moon are expected to expand and contract that distance. GRAIL scientists will use these accurate measurements to define the moon’s gravity field. The data will allow mission scientists to understand what goes on below the surface of our natural satellite. This information will help us learn more about how the moon, Earth and other terrestrial planets formed.
The mission comes as NASA has sought to increase interest in the space program, following a series of substantial budget cuts. The space agency announced earlier this year that it would join with a number of private companies in order to devise a replacement for the now retired space shuttle.
The next mission milestone occurs Sunday when GRAIL-A’s mirror twin, GRAIL-B, performs its own main engine burn to place it in lunar orbit. At 3 p.m. PST (6 p.m. EST) today, GRAIL-B was 30,018 miles (48,309 kilometers) from the moon and closing at a rate of 896 mph (1,442 kph). GRAIL-B’s insertion burn is scheduled to begin tomorrow at 2:05 p.m. PST (5:05 p.m. EST) and will last about 39 minutes.
JPL manages the GRAIL mission for NASA’s Science Mission Directorate at the agency’s headquarters in Washington. The GRAIL mission is part of the Discovery Program managed at NASA’s Marshall Space Flight Center in Huntsville, Ala. Lockheed Martin Space Systems in Denver built the spacecraft.
NASA’s previous moonshot occurred in 2009 with the arrival of the Lunar Reconnaissance Orbiter and a companion spacecraft that deliberately crashed into the south pole to measure the amount of water in a crater. Future lunar missions will be unmanned after the Obama administration last year scrapped a plan to send astronauts back in favor of going to an asteroid as a stepping stone to Mars.