NASA’s CAPSTONE performed its fourth of six planned trajectory correction maneuvers on Thursday, October 27, setting the stage for the spacecraft’s arrival to an elliptical halo lunar orbit in less than two weeks.
The 55-pound cubesat fired its propulsion system for 220 seconds during the planned maneuver, Advanced Space, the private company managing the mission for NASA, explained in an update. The mission’s fourth trajectory correction maneuver transpired late last week, moving CAPSTONE ever closer to its ultimate destination: the lunar Near Rectilinear Halo Orbit (NRHO). The probe is expected to reach its operational orbit on November 13.
Advanced Space says the probe was 308,076 miles (495,800 kilometers) from Earth at the time of the maneuver, or about 69,000 miles (111,000 km) past the Moon. NASA and its partners are using the ballistic lunar transfer (BLT) technique to transfer CAPSTONE to NRHO which, though convoluted and long, is highly fuel-efficient. The spacecraft launched on June 28 and has been flying solo in space for the past four months.
Once in NRHO, the $33 million cubesat will enter into uncharted territory, as no spacecraft has ever worked in this highly elliptical orbit—one intended for the upcoming Gateway space station. CAPSTONE, short for Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment, will test this orbit for NASA, setting the stage for Gateway and the upcoming Artemis missions to the Moon.
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The latest trajectory correction maneuver “confirms the preparation, extensive analysis, teams working together and continued hard work to allow this mission to remain successful, especially following the recent anomaly,” Alec Forsman, CAPSTONE mission operations manager at Advanced Space, said in the update.
Indeed, the mission threatened to go sideways after the third course correction maneuver on September 8. CAPSTONE, built by Terran Orbital, lost axis control and began tumbling, a serious situation that threatened to derail entire the mission. Unable to point its solar panels toward the Sun, CAPSTONE wasn’t able to fully recharge.
The recovery team eventually traced the problem to a partially opened valve on one of the spacecraft’s eight thrusters, which the team remedied with a recovery sequence transmitted to CAPSTONE a full month after the anomaly. As NASA adds: “The mission team will design future maneuvers to work around the affected valve, including the two remaining trajectory correction maneuvers scheduled before CAPSTONE’s arrival to orbit at the Moon.”
With the fourth trajectory correction maneuver complete, CAPSTONE is now days away from reaching its orbit around the Moon and entering into the demonstration phase of the mission. The probe will spend at least six months gathering operational data and testing autonomous spacecraft-to-spacecraft navigation capabilities, the latter of which could eventually lead to spacecraft capable of determining their own locations in space without outside help. An early successful test, in which NASA’s Deep Space Network facilitated a conversation between CAPSTONE and the agency’s Lunar Reconnaissance Orbiter, is a promising start to the Cislunar Autonomous Positioning System demonstration, as Advanced Space calls it.