GOMX-4B

The mission

The GomSpace Express-4B (GOMX-4B) was a 6U CubeSat aimed at flight demonstrating key nano-satellite constellation related technologies, including inter-satellite links and propulsion technologies when flying in tandem with the GOMX-4A CubeSat, developed by GOMSpace for the Danish Ministry of Defence. 

Platform: 6U CubeSat.
Payload: software-defined radio in multiple RF bands, Hyperscout compact hyperspectral imager, star tracker, ESA Chimera experiment.
Programme: General Support Technology Programme (GSTP).
Contractor: GOMSpace Denmark. 

Mission description

The GOMX-4B platform was equipped with a miniaturized propulsion system and S-band inter-satellite link transceiver, as well as a hyperspectral imager and was launched and operated together in a tandem mission with the GOMX-4A CubeSat which was developed under a Danish national Ministry of Defence programme. GOMX-4A and 4B built upon the platform/payload technologies previously developed and demonstrated with the 3-unit GOMX-3 CubeSat IOD mission (reconfigurable software defined radio, 3-axis attitude control system) deployed from ISS in October 2015. 

The GOMX-4B mission took advantage of the GOMX-4A project in order to de-risk miniaturized technologies and demonstrate system-level capabilities that enable the controlled deployment, operation and maintenance of future operational constellation systems based on CubeSats. In particular, GOMX-4B demonstrated an on-board cold gas propulsion subsystem and related AOCS subsystem in order to successfully perform along-track station acquisition manoeuvres relative to GOMX-4A up to separation distances representative of an operational constellation (approximately 2000-4000 km) for the first time. The relative attitudes of the two satellites were also controlled to demonstrate differential drag station-keeping manoeuvres. S-band Inter-Satellite Link (ISL) transceivers were embarked on both GOMX-4A and GOMX-4B,  and successfully operated at these long distances in order to demonstrate for the first time low latency relay of payload data from a CubeSat to ground stations, which were located in Danish territory. New direct spread spectrum techniques were developed during the mission, uplinked to the ISL transceivers and successfully tested in flight, highlighting the flexibility of the software-defined radio technology. 

Additionally, since the GOMX-4B 6U CubeSat platform had some available resources to accommodate third party technology payloads, the HyperScout miniaturised hyperspectral imager (developed by Cosine Research b.v. under a separate GSTP activity) was embarked and successfully acquired the first hyperspectral imagery acquired by a CubeSat at several locations on Earth. Additional payloads included a radiation hardness assurance board developed by ESA/ESTEC, and an experimental star tracker from Innovative Solutions In Space b.v. 

Mission status

Launch: February 2018.
Status: operational.