Rather than engaging in active debris removal of real space debris, the RemoveDEBRIS mission plan is to test the efficacy of several ADR technologies on mock targets in low Earth orbit. In order to complete its planned experiments the platform is equipped with a net, a harpoon, a laser ranging instrument, a dragsail, and two CubeSats. The experiments are as follows:
Net experiment - One of the CubeSats, called DebrisSat 1, will deploy a balloon meant to simulate a piece of space debris. From a short distance away, the RemoveDEBRIS satellite will attempt to capture the debris in a net and then manoeuvre this package to fall into Earth's atmosphere and burn up.
Vision-based navigation - The other CubeSat, called DebrisSat 2, will be released and the RemoveDEBRIS satellite will undergo a series of manoeuvres in order to obtain data and images using both lidar and optical cameras.
Harpoon and deployable target - A harpoon connected by a tether will be fired at a plate attached to an arm extending from the RemoveDEBRIS platform itself.
Dragsail - After the conclusion of the other experiments the satellite will deploy a large sail, which will act in a similar fashion to an air brake. The dragsail will bring RemoveDEBRIS from the relatively low orbital altitude of the space station into the planet's atmosphere to safely disintegrate.
Design
Platform
The RemoveDEBRIS platform was based on a SSTL X50 Structure that had been customised for deployment from the International Space Station. The platform hosted all the experimental payloads as well as providing power, data and control for the mission. A high degree of autonomy was built in using time-tagged commands to allow experiments to be run out of sight of the groundstation.
CubeSats
DebrisSat 1
The DebrisSat 1 was built by engineers and students at the University of Surrey and was based on a 2U CubeSat measuring 100 × 100 × 227 mm. 1U of the satellite contained the power and avionics to power the payload. The payload contained an inflatable designed to provide a large target area for the next experiment. A Cold Gas Generator was used to inflate six aluminium booms to provide a frame. Small aluminium sails attached to the end of the booms would then be deployed during the inflation.
DebrisSat 2
The DebrisSat 2 is also based on a 2U CubeSat with two deployable panels solar panels and communications. The spacecraft contained a GPS receiver as well as an inter-satellite link to provide location and attitude data back to the platform to assess the VBN camera performance. The avionics were based on the QB50 avionics stack developed by the Surrey Space Centre and Electronic Systems Laboratory at Stellenboch University. In addition the spacecraft also tested out a low-cost UART camera which was able to beam back pictures back to the platform as it separated. DebrisSat 2 deorbited 30 May 2020.
Timeline
Launch
After final system end-to-end and environmental testing, the RemoveDebris spacecraft was shipped to Nanoracks in Houston and then onto the launch site at the Kennedy Space Centre in Florida. The spacecraft was placed in an ISS cargo transfer bag and placed in the pressurised section of the CRS-14 SpaceX Dragon Spacecraft. The Dragon resupply mission with RemoveDEBRIS onboard was launched 2 April 2018, arriving at the ISS on 4 April. The RemoveDebris spacecraft was unloaded from the capsule. NASA Astronauts Drew Feustel and Ricky Arnold removing the platform handling panels, completed final preparation and loaded the satellite into the Japanese Experiment Module airlock on 6 June 2018. An airlock cycle was performed on 19 June 2018 and RemoveDEBRIS moved outside the JEM via the airlock slide table. The spacecraft was grasped by the Kaber interface on the Mobile Servicing SystemSpecial Purpose Dexterous Manipulator and placed in the deployment position.
Deployment
Deployment of the satellite from the station's Kibo module via robotic Canadarm-2 took place on 20 June 2018. At approximately 100 kg, RemoveDEBRIS is the largest satellite to have ever been deployed from the ISS. The platform contained two CubeSat deployers from ISISpace. The full lifespan of the mission from launch to re-entry is estimated at 1.5 years.
Net experiment
On 16 September 2018, it demonstrated its ability to use a net to capture a deployed simulated target.
VBN experiment
On 28 October 2018, DebrisSat 2 was deployed at 06:15UTC. The VBN camera on the platform took 361 images of the spacecraft crucial to determining the performance of the camera system. Position and attitude data from DebrisSat 2 was transmitted back to the platform providing ground truth for the experiment. DebrisSat 2 also forwarded low resolution photos of the deployment to the platform from its own vantage point.
Harpoon experiment
On 8 February 2019, SSTL demonstrated the RemoveDEBRIS harpoon which was fired at a speed of 20 metres per second penetrating a simulated target extended from the satellite on a boom.
Dragsail experiment
The deployment of the dragsail was targeted for 4th March. After the deploy command had been sent, no expected changes in spacecraft behaviour were detected. After an investigation it was determined that the most likely result was a partial or failed deployment of the inflatable boom which prevented the sail from deploying. Lessons learnt from this attempt were put into practice for two new dragsails that were deployed on the Spaceflight SSO-A mission.
