On-Orbit Servicing is a complex and risky operation, but a number of space companies already have contracts with satellite operators for servicing missions.

Current European communication missions are still not prepared to be serviced, but in order for them to go ahead, this ability will become necessary in the near-future. Preparing a satellite to be serviced means not only including in its design a ‘grapple fixture’ and an interface to allow for fuel transfer, but the satellite must also be in a cooperative state during rendezvous and capture by the service provider.

As a first step in refuelling, the TRP study ASSIST developed an interface to enable the transfer of chemical propellant up to TRL 4. However, most future satellites will employ electric propulsion using Xenon fuel. As such, there is the need to test and continue developing this interface to ensure it is compatible with other propellants.

hArmonised System Study on Interfaces and Standardisation of fuel Transfer (ASSIST) concept for fuel transfer between satellites
Credits: GMV

Furthermore, the serviced spacecraft could also require dedicated markers or patterns in specific locations, or it may need new attitude and pointing abilities to make rendezvous and capture possible. Thus, there is the need to define guidelines for future telecom satellites which describe all of the changes required to enable servicing and refuelling.

The Invitation To Tender for this subject is published in ESA’s online tendering system EMITS. Industry interested in this study are invited to read the Statement of Work via the following link:


The objective of this activity is to perform a systematic assessment of what  a satellite needs in order for it to support xenon fuel transfer, and to mature the respective technology to TRL 5. The assessment will cover the impacts  on operations (ground segment and space segment), the functionality of the client in support of the complete service operation, including both capture and fuel transfer, and the integration of fuel transfer equipment within the propulsion system. At the end of the study, a set of ‘Servicing Guidelines’ for telecom platforms covering rendezvous, capture, servicing (e.g. refueling) and separation will be derived.

More information:


Closing date: 12/11/2019

Duration of the contract: 12 months

Price range: > 500 kE