When Alphasat was launched on 25 July 2013 from the European Spaceport in Kourou, a programme of hosted payloads was one of the mission’s objectives. The initial three-year in-orbit demonstration period having been completed, ESA and Inmarsat, the satellite operator, together with the hosted payload providers will kick off an extension of the programme on 1 January 2017 for another three years, covering the period 2017-2019.
Europe’s largest telecoms satellite to date, Alphasat was developed in a Public Private Partnership between ESA and Inmarsat. The mission’s primary purpose was to complement Inmarsat’s existing satellite fleet. Located at 25 degrees East, Alphasat’s L-band payload provides Inmarsat with extra commercial capacity and additional services over Europe, the Middle East and Africa. The programme included the development of highly innovative payload technologies, such as an advanced digital integrated processor allowing flexible allocation of capacity by digital channelisation and beamforming.
Another major goal of the mission was to fly the new high-power satellite platform, called Alphabus, which was developed by Airbus DS and Thales Alenia Space, through a joint initiative between ESA and CNES, the French space agency, undertaken within frame of the ARTES programme. The success of this aspect of the mission demonstrates Europe’s ability to meet operators' needs in the high-power segment, which represents a growing market in terms of sales.
In addition to this, approximately 20% of the spacecraft’s resources were dedicated to four hosted payloads, also called Technology Demonstration Payloads (TDPs), which were provided by ESA. In agreement with Inmarsat, these payloads will continue to be in operation during the coming three years.
Laser communication and Ka-band downlink
The Laser Communication Terminal (LCT) payload provides Low Earth Orbit to Geostationary Orbit optical communications at up to 1.8 Gbps. A Ka-band transmitter then relays the data to a ground station.
The Alphasat LCT has established and demonstrated the first LEO to GEO optical link with this advanced technology, opening the path to the European Data Relay System (EDRS). It has been used for testing and demonstration purposes using two Sentinel satellites from the Copernicus Earth Observation constellation, as LEO counterparts. The Sentinels are equipped with on-board laser terminals, similar to the one flying on Alphasat. They have recently started operational services with EDRS.
During the extension period, the LCT will continue to be used for in-flight characterization of the performance of optical intersatellite communication links. It will also be used to better understand the impact of the atmosphere on laser links to optical ground stations. Using laser links for additional applications, such as communications with Remotely Piloted Aircraft (RPAs) will be further explored.
Q/V-band communication and propagation
Developed by Space Engineering and Thales Alenia Space with supported from ASI, the Italian Space Agency
A Q/V-band communication repeater, called the Aldo Paraboni Payload, explores the use of these frequencies for future applications. In parallel, experiments with propagation beacons in Q- and Ka-bands measure the effects of the Earth’s atmosphere on radio waves.
The Aldo Paraboni Payload flying onboard Alphasat is complemented by three communications ground stations, two in Italy supplied by ASI and one in Austria procured with support from FFG, the Austrian Research Promotion Agency. In addition, the network of beacon reception stations has grown from 3 to 18 and now spans the whole of Europe, demonstrating the success of this mission within the communications research community.
During the extension period, scientific and communications experiments will continue to be undertaken which will lead to the better understanding of these high frequency bands. These developments will also be relevant for the development of propagation models for future telecommunications satellite Q-, V- and W- band systems and non-geostationary Ka-band systems.
An advanced Star Tracker with active pixel detection was included as a hosted payload to gain early flight heritage for this new product. It is capable of very accurate and autonomous attitude acquisition. The sensor is highly resilient to the radiation experienced in geostationary orbits. In-orbit validation of the star tracker has given a tremendous boost to the company’s sales on the world market.
During the extension period, the long-term health and performance of the star tracker will continue to be monitored by comparing star patterns each geosynchronous day.
Developed by EFACEC-Evoleo, with support from Portugal
The Environment Effects Facility payload tests next-generation electronic components (optical transceivers, GaN transistors, and flash memories) in the radiation environment of a geostationary orbit. An energy selective particle spectrometer measures radiation levels in parallel. The end goal of this payload is to gain experience in orbit with these new components, allowing their use in the next generation of spacecraft.
During the extension period, tests will continue on sensitivity to space radiation. This is particularly important, for instance, to better correlate the real degradation of optical transceivers in space with ground testing in a simulated environment.
“The first three years of operations have shown that ambitious hosted payloads to demonstrate new technologies in flight can be successfully embarked on a commercial spacecraft,” says ESA’s Philippe Sivac, Large Platform Mission programme manager. “First seen as a programme opportunity, the hosted payloads have become a mission in their own right, each with an active research and development community, taking full benefit of the in-orbit and on-ground infrastructure. We look forward to the next three years of exciting results from our hosted payloads.”
"The Alphasat set of hosted payloads is a great example of the flexibility of the PPP model, demonstrating that the embarked technology demonstration payloads are also operationally used to the maximum extent possible," says Magali Vaissiere, Director of Telecommunications and Integrated Applications at ESA. "Both the commercial operator as well as ESA and its institutional partners are able to exploit the capabilities of this powerful spacecraft in highly synergistic ways, to the benefit of the space community as a whole."