The primary objective of ESA under the Alphasat Programme Line is to facilitate an early first flight, and in-orbit validation of the Alphabus platform, currently under development with industry. Following an extensive evaluation process, ESA selected Inmarsat Global Ltd geomobile mission for this first flight opportunity.
Both ESA and Inmarsat will bring substantial funding to accomplish the mission.
In addition to the operational payload, ESA is also providing four Technology Demonstration Payloads (TDPs) for embarkation on the Alphasat. These will constitute approximately 15% of the total payload embarked.
Technology Demonstration Payloads
Following several technology studies and preliminary accommodation activities four TDPs have been selected for flight on the Alphasat. These comprise;
- An advanced Laser Communication Terminal to demonstrate GEO to LEO communication links at 1064nm,
- A Q-V Band communications experiment to assess the feasibility of these bands for future commercial applications,
- An advanced Star Tracker with active pixel detector ,
- An environment effects facility to monitor the GEO radiation environment and its effects on electronic components and sensors.
A new activity related to the ground segment of TDP5 is under preparation with Joanneum Research (Austria) in coordination with ASI (Italy) who is responsible for the TDP ground operations. It consists of the definition, selection, installation and operation of a high-performance Q/V-band ground station with tracking antenna on a fixed location in Graz.
- In orbit-validation of the Alphabus product line, on a commercial mission,
- Completion of the environmental qualification testing of the Alphabus product line,
- Opportunity for demonstration of new European technologies.
Inmarsat “Geomobile” Mission
Following the successful implementation of the Inmarsat IV satellite series, Inmarsat is now able to deliver the new BGAN (Broadband Global Area Network) family of services which provides a wide range of high data rate applications to a new line of user terminals for aeronautical, land and maritime markets.
With the Alphasat mission Inmarsat will extend the capabilities of this Geo–mobile infrastructure, both in terms of performances and capacity, resulting in an enhancement in the current services and additional capacity for new services.
The Alphasat mission definition is based around two main service types;
- BGAN directional (as currently provided by Inmarsat IV),
- BGAN Omni-directional (including handheld services).
Alphasat will be capable of accessing the additional 2x7 MHz of L band spectrum allocated at the WRC-03, which were not available to the Inmarsat IV satellites, when originally specified. It will be positioned at 25 degrees East, covering Europe, Middle East, Africa and parts of Asia.
Implementation of this Geo-mobile application necessitates the adaptation of the nominal Alphabus platform design to allow a 90 degree rotation of the satellite flight orientation (for better accommodation of the feed/reflector configuration) and the accommodation of the large deployable reflector. Both these adaptations are offered as options in the future Alphabus portfolio, demonstrating the flexibility of this platform.
- Alphabus Service Module in geomobile configuration, compatible with Proton 4 m fairing,
- Repeator Module split in 2 halves, for ease of payload accommodation,
- Implementation of payload integrated processors providing payload flexibility through coverage and power reconfiguration capabilities,
- 11 m diameter deployable reflector,
- Total launch mass: more than 6 tons,
- Total Electrical power: 12 KW.
Payload / Repeater Module
The Inmarsat extended L- band (XL) payload will support advanced geomobile communications and augment Inmarsat's Broadband Global Area Network (BGAN) service with its coverage centred over Africa and providing additional coverage to Europe, the Middle-East and parts of Asia.
Development of the Inmarsat operational payload equipments is progressing well. For the vast majority of the equipments targeted for the Payload, Equipment qualification models (EQM) testing is complete and about 75% of the payload equipment is either already delivered or being shipped to Portsmouth for integration on North and South Half Repeater Module structures.
Despite the good progress, significant challenges still remain related to the development of the critical elements: the Integrated Processor, the Calibration and Frequency Generator Units.
The Payload Repeater Module is planned to be shipped to Astrium Toulouse in December 2010.
Technology Demonstration Payloads
The Technology Demonstration Payloads (TDPs) consist of:
TDP1: an Advanced Laser Communication Terminal to demonstrate GEO to LEO communication links at 1064nm (supplied as customer furnished item by DLR):
TDP5: a Q-V Band communications experiment to assess the feasibility of these bands for future commercial applications
TDP6: an Advanced Star Tracker with active pixel detector
TDP8: an Environment effects facility to monitor the GEO radiation environment and its effects on electronic components and sensors
The development of the TDPs is progressing well with flight hardware being manufactured and tested. Each TDP development offers unique challenges but all are progressing towards the successful embarkation on the Alphasat satellite.