CNES mission

As partner and passenger in the PRISMA mission, CNES participates with an experiment named "FFIORD" - Formation Flying In Orbit Ranging Demonstration. The main objective of FFIORD experiment is to perform a first in-orbit demonstration of the FFRF sub-system. The main objectives of this demonstration are twofold:

Validate the FFRF subsystem in orbit

Validation the FFRF subsystem will consist in performing functional tests and performance evaluation of the FFRF sensor so as to ensure that the instrument's behavior is consistent with the specifications. The functional tests will focus on the following items:

RF signal acquisition
Integer Ambiguity Resolution (IAR) procedure
Power management
Antenna management (manual or automatic)
Communication data rate selection
Inter Satellite Link (ISL)

These tests need to be performed at different relative distances and relative attitudes especially for the RF signal acquisition and the IAR procedure that may show some sensitivity to these parameters. The performance evaluation will consist in collecting data in geometric and dynamic conditions that cover as much as possible the FFRF sensor measurement domain (range < 30 km, v <0.5 m/s, dq/dt < 5°/s).

This FFRF subsystem validation will include work sessions spread all along the mission timeline. These work sessions will be decomposed in two groups with different availability of PRISMA resources:

The FFRF sensor is activated as a secondary experiment thus offering the capability to perform extensive data collection in Open Loop mode
The FFRF sensor is activated as a primary experiment and the MAIN satellite can be requested to follow a FFIORD dedicated relative attitude and orbit trajectory.

The target satellite TANGO followes its initial intertial orbit. The chazer satellite MANGO moves around TANGO to simulate different stages of a Formation Flying scenario

The primary experiment phase will consist of performing a ground-controlled succession of separation and approach movements with different relative translation rates in order to minimize the fuel usage.

Conduct formation flying experiments using the FFRF sensor and the CNES on-board software.

The RF based formation flying experiments makes use of the dedicated CNES Flight Software (FSW), and includes the following demonstrations, all relevant for future formation flying missions:

Proximity operations:

Station-keeping at different distances and offset positions from the orbit track (VBAR)
Low speed translations in-plane and out of plane

Rendezvous
Collision avoidance (auto. transfer on Football orbit in 1 or 2 manoeuvres)
Stand-by on a relative orbit
Recovery after system anomaly

These formation flying experiments will be run in closed loop. The experiment will last approximately 17 days.