The MTG mission (Meteosat Third Generation) is made up of six satellites installed on two different platforms, MTG-I and MTG-S which, in turn have two key instruments: on the one hand, the Flexible Combined Imager (FCI) and, on the other hand, the InfraRed Sounder (IRS), each one integrated into its respective platform, being their main purpose to carry out complementary observation tasks.

The SCAN ASSEMBLY (SCA) for both, FCI and IRS missions, provides to the six satellites, the means to accurately scan all Earth surface. It is composed of the Scan Mechanism (SCAU) and the Scan Electronics (SCAE) containing the actuator drive electronics, the control, algorithms and the related software and firmware. The sweeping or scanning mechanisms are key elements of the FCI and IRS in terms of optical quality and the accuracy and pointing stability of the M0 mirror in both telescopes. They generate high resolution images through sweeping, thereby eliminating the rotational movement of the satellite (spinning) that currently occurs in previous METEOSAT generation (MSG).

SCAU (Scan Assembly Unit): two axis scan mechanism mounted on flexural pivots that moves the instrument M0 mirror. Provided with:

• Voice coil actuators.
• 25 bits Encoders working in close control loop.
• An attenuation damping system to maintain its performances even being present the disturbances provided by the satellite.
• It operates under hard specifications and even under sun intrusion conditions.
• A motorised releasable launch locking device on SCAU to withstand the launch loads.

Some remarkable figures of the SCAU are:

• Operation range: about +/-5º elevation and +/-10º azimuth.
• Accuracy: some micro-rad.
• Dynamic Pointing Stability: better than 1 micro-rad.
• Thermo-elastic Stability: about 5 micro-rad.
• Mirror size: 350 x 500 mm.
• Optical performance: better than 16 nm WFE.

SCAE (SCan Assembly Electronics): electronic box in charge of controlling the movement of the SCAU using specific control algorithms, monitoring accurately the angular position of each axis and providing 1553 and Spacewire communication capability.

The MTG mission (Meteosat Third Generation) is made up of six satellites installed on two different platforms, MTG-I and MTG-S which, in turn have two key instruments: on the one hand, the Flexible Combined Imager (FCI) and, on the other hand, the InfraRed Sounder (IRS), each one integrated into its respective platform and the main purpose of which is to carry out complementary observation tasks.

The Calibration and Obturation Mechanism (COM) for the FCI proposed by Sener is similar to a wheel of filters that turns to position the chosen element and into which the optical devices are integrated, the black body, the filters and the shutter. For its part the Calibration and Obturation Mechanism (COM) for the IRS has a mirror mechanism which, by turning on its axis, selects between calibration with the black body, calibration with the neutral density filters, the shutter or the view position.

• Features:
• Enables Visual and NIR calibration of the instrument, with MND filters (Metallic Neutral Density).
• Allows IR calibration with BB (Black Bodies).
• Allows light-path obturation (quickly, to prevent sun intrusion).
• Allows free access during viewing.
• Executes predefined transitions between functions.
• Locks the mobile part during launch and releases it after launch.
• Executes heat control of the black body.
• All of this, whilst maintaining the structural integrity and stability.

The verification of avionics and especially of the AOCS (Attitude and Orbit Control System) or GNC subsystem (Guidance, Navigation and Control) is a vital operation during the flight segment of all space systems.

Until now, most test benches have been designed specifically for each project. However, SENER now has a reusable, flexible and scalable system, that can be adjusted quickly and incorporated in any verification campaign. The generic AOCS SCOE (Special Check Out Equipment) offers a real-time simulator with the features and capabilities required for proper verification of the AOCS.

Instantiation of the AOCS SCOE for the Meteosat Third Generation (MTG)

Sener has developed, integrated and supplied five AOCS SCOE systems for six Meteosat Third Generation (MTG) satellites.

The main aim of the AOCS SCOE it is to conduct open-loop and closed-loop testing of the AOCS in each stage of development of MTG. For this purpose, it provides interfaces both for the simulation and stimulation of the sensors and actuators incorporated in the AOCS. In addition, it reproduces in real time the dynamic and kinematic conditions and the effects produced by the physical environment on the satellites.

This equipment allows the testing and verification of the Meteosat Third Generation (MTG) sweep system. It consists of the electronic testing equipment, the mechanism simulation and the mechanism testing equipment.

The comprehensive user interface configures the tests and provides observability during the tests and reproduces the complementary function of the interfaces of the testing equipment.

This same equipment was used to fully verify the software of MTG SCA.