First Commercial Lunar Orbiter Successfully Completed All Operational Objectives – CAPSTONE™ Continues Moon Operations to Inform Future Missions

Advanced Space’s pioneering commercial satellite continues to operate beyond its expected 18-month contracted mission, which was originally supposed to end this month. Begun with a mission to demonstrate the Cislunar Autonomous Positioning System (CAPS™) software in the Near Rectilinear Halo Orbit (NRHO) that will be used by the Gateway lunar space station, the Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment (CAPSTONE™) spacecraft will continue to demonstrate lunar operations and navigation technology, along with other capabilities. The spacecraft has enough propellant onboard to function well past its original mission date.

Bradley Cheetham, Advanced Space’s President and CEO,

“It’s amazing that we have reached this point. In seven years, CAPSTONE has gone from a bright idea by a small business to a mission that continues to blaze new trails well past its expected end date. I couldn’t be prouder of this team and our NASA and industry partners like Terran Orbital, who built the spacecraft.”

The CAPSTONE mission has accomplished a tremendous amount since entering the NRHO 18 months ago. The spacecraft has achieved all of its Primary Mission goals, which began with testing a low-energy transfer from Earth to the Moon. On the way to the Moon, it survived a communications outage and then a stuck thruster, which caused it to spin uncontrollably for several weeks.

Mission(s) Accomplished

CAPSTONE has accomplished all of its primary objectives, beginning with demonstrating flight operations within NRHO, which is a three-body orbit (i.e., the body of the spacecraft is affected by the gravity of the Earth and Moon). These successful operations included precise measurements of its change in velocity (delta-V) and actual location along its 9:2 synodic orbit. The 9:2 orbit means the spacecraft completes approximately 9 orbits around the Moon for every 2 sidereal orbits the Moon makes around the Earth. This timing results in a 6.5-day lunar orbit that enables CAPSTONE to avoid most eclipses by the Earth, keeping the solar panels in the sun and charging.

Next, the mission was designed to provide useful information to NASA on how to maneuver and operate in NRHO. This information is important because NASA plans to orbit the Lunar Gateway space station in that orbit in the near future as part of the Artemis program.

Lastly, and perhaps most importantly, the mission was designed to test our company’s CAPS software, which crosslinks CAPSTONE’s radio with other spacecraft—in this case, NASA’s Lunar Reconnaissance Orbiter (LRO)—to determine each spacecraft’s absolute positions compared to the Earth-Moon system.

CAPSTONE’s Primary Mission began after a second correction maneuver inserted the spacecraft into the orbit. Since then, the microwave-sized CubeSat has completed 83 orbits in NRHO and performed 25 maneuvers to maintain this orbit despite the still-stuck thruster. The spacecraft also has endured 18 eclipses ranging from 75 minutes to less than one.

In addition to its original mission objectives, CAPSTONE is helping NASA and other customers test future communication, navigation, and software technologies for operating on or in the vicinity of the Moon. The spacecraft will continue to demonstrate critical technologies that will support future missions to the Moon until fuel constraints require Advanced Space to dispose of the spacecraft on the surface of the Moon.

CAPS – Testing for the future

CAPSTONE tested navigation technology akin to Earth’s global positioning system (GPS). This technology, CAPS, Cislunar Autonomous Positioning System, was developed by Advanced Space. Through working with the Lunar Reconnaissance Orbiter (LRO) team, Advanced Space has been able to collect crosslink measurements between CAPSTONE and LRO successfully five different times during its mission so far. During these experiments, the CAPSTONE spacecraft sends a navigation signal to LRO, which was subsequently sends back to CAPSTONE. From the returned signal, CAPSTONE is able to compute its range and trajectory Doppler shift to estimate its position. This was a primary objective for the mission which sought to demonstrate the CAPS technology providing autonomous onboard navigation. Using the gathered data, the team will look to improve subsequent crosslink demonstrations and continue to work towards demonstrating operational feasibility. In the future, additional data types will be demonstrated and incorporated into CAPS to deliver navigation knowledge to users in orbit and on the surface of the Moon.

In addition to conducting multiple two-way crosslinks, CAPSTONE has performed one-way uplink measurements on every single pass since December from every station of NASA’s Deep Space Network (DSN), including the site at Morehead State University. These measurements, developed in collaboration with NASA’s Jet Propulsion Laboratory in Southern California, are providing tremendous amounts of data to evaluate and mature one-way uplink data processing for onboard navigation. In connection with these measurements, we also conducted several experiments related to when and how we capture this data to understand and isolate effects such as thermal transients on the stability and performance of the onboard chip-scale atomic clock (CSAC).

As if that were not enough, CAPSTONE also has become a software test bed for operating machine-learning programs like SigmaZero in a lunar orbit environment to help identify spacecraft anomalies. Advanced Space plans to employ CAPSTONE while it’s up there as the only space-based test server operating at the Moon.

What’s next

CAPSTONE’s adventures have not ended, either. While testing new capabilities, the spacecraft also needs to cope with the natural hazards around the Earth-Moon system. It has ridden out eclipses of the Sun by the Moon that were as long as nearly 75 minutes. And just recently, it rode out the extreme coronal mass ejection put out by the Sun.

As CAPSTONE continues to operate past its expected program date, it will continue to collect additional crosslink measurements and one-way uplink measurements from the Earth as well as demonstrate other software to advance development in spacecraft autonomy.

CAPSTONE also will be used as a test bed for Advanced Space’s turn-key flight dynamics ground software (FDS), which provides rapid-turnaround navigation and maneuver planning for deep space and cislunar missions.