CAPSTONE (Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment)

Demonstrate spacecraft-to-spacecraft navigation and enter Lunar near-reactilinear halo orbit to verify its feasibility for the Gateway lunar orbiting outpost.

Designed to go into a near-rectilinear halo orbit around the Earth to closely match the Moon's orbit. The primary objectives are to demonstrate spacecraft-to-spacecraft navigation and to enter this orbit to verify its feasibility, to gain experience for future flights planning to use similar orbits, and as a precursor to the possible Gateway lunar orbiting outpost.

A deployable dish antenna is used for communication. Propulsion is provided by a monopropellant hydrazine reaction control system. It uses eight 0.25 N thrusters, four for translational thrust and four for rotational thrust. It will carry approximately 3.2 kg of hydrazine in a machined aluminum tank.

It will be launched on a Rocket Lab Electron booster from NASA Wallops Flight Facility into a 250 km circular Earth orbit, the Photon upper stage will perform a series of orbit-raising maneuvers to put CAPSTONE into a trans-lunar trajectory. CAPSTONE will travel 3 months under its own propulsion. It will then enter a near-rectilinear halo orbit, in which the spacecraft orbits the Earth along with the Moon, and will come within about 1600 km of one pole and then 7 days later pass roughly 70,000 km above the other pole. It will continue in this orbit for at least six months, testing communications with the Lunar Reconnaissance Orbiter (LRO), already in orbit around the Moon, and ground stations on Earth. It will also use data from communications with LRO to determine its position.

The orbit, formally known as a near rectilinear halo orbit (NRHO), is significantly elongated. Its location at a precise balance point in the gravities of Earth and the Moon, offers stability for long-term missions like Gateway and requires minimal energy to maintain. CAPSTONE’s orbit also establishes a location that is an ideal staging area for missions to the Moon and beyond.

To test these new navigation capabilities, CAPSTONE has a second dedicated payload flight computer and radio that will perform calculations to determine where the CubeSat is in its orbital path. Circling the Moon since 2009, NASA’s Lunar Reconnaissance Orbiter (LRO) will serve as a reference point for CAPSTONE. The intention is for CAPSTONE to communicate directly with LRO and utilize the data obtained from this crosslink to measure how far it is from LRO and how fast the distance between the two changes, which in turn determines CAPSTONE’s position in space.

This peer-to-peer information will be used to evaluate CAPSTONE’s autonomous navigation software. If successful, this software, referred to as the Cislunar Autonomous Positioning System (CAPS), will allow future spacecraft to determine their location without having to rely exclusively on tracking from Earth. This capability could enable future technology demonstrations to perform on their own without support from the ground and allow ground-based antennas to prioritize valuable science data over more routine operational tracking.

Mission objectives:

• Verify the characteristics of a cis-lunar near rectilinear halo orbit for future spacecraft.
• Demonstrate entering and maintaining this unique orbit that provides a highly-efficient path to the Moon’s surface and back.
• Demonstrate spacecraft-to-spacecraft navigation services that allow future spacecraft to determine their location relative to the Moon without relying exclusively on tracking from Earth.
• Lay a foundation for commercial support of future lunar operations.
• Gain experience with small dedicated launches of CubeSats beyond low-Earth orbit, to the Moon, and beyond.

~4 months in deep space to arrive at its target insertion into the  NRHO via a low-energy, deep space transfer using a hydrazine propulsion system. Insertion into the NRHO occurred on November 13, 2022. Scheduled to orbit this area around the Moon for up to 18 months to  understand the characteristics of the orbit and perform technology demonstrations.

CAPSTONE has successfully operated in the NRHO since 11/13/22 (167 days)

• All six(6) Orbital Maintenance Maneuvers (OMM’s) have successfully executed as planned. Multiple planned OMM’s have been cancelled cancelled due to process of stepping down DV to find a lower bound threshold.
• OMM cadence reduced due to minimum OMM DV based on the updated Terran controller implemented for the post-TCM-3 valve anomaly.
• Due to updated maneuver performance, further threshold reductions are expected to reduce the minimum OMM < 5 cm/sec.
• Two anomalies has occurred since NRHO insertion: Loss of commanding on uplink occurred on Jan. 26th and Feb 17. Suspect SEU on the Iris firmware as the root cause. Commanding restored on Feb 6th and Mar 1st when Command Loss Timer reset the spacecraft.
• First CAPS pass attempt occurred on 18 Jan. LRO received a signal, but no ranging data was observed. Two additional passes have been successfully executed with data collected but the ranging data was now well characterized.
• Next CAPS pass attempt (lower range to LRO) is planned for 5/9/23. Working the TUI on adjustments to the ranging modulation to improve the measurement quality.
• CAPS SW Version 0.5 continues development and will be part of potential in flight SW updates to improve the accuracy of the navigation estimate and correct issues observed in the initial experiment’s results.

• THRUSTER - Stellar Exploration