|The Astra 2D Satellite
|The Astra 2D satellite is no longer in service at 28.2° east, all frequencies and channels have been transfered to Astra 1N and Astra 2F.
Astra 2D is one of the Astra communications satellites owned and operated by SES, and located at 28.2° east in the Clarke Belt. It is a Hughes HS-376 craft, and was launched from the Guiana Space Centre in December 2000 to join Astra 2A and Astra 2B at 28.2°E, where it has remained for its active life.
Astra 2D Specifications
16 active 39-w TWTAs for DTH
Receivers 4 for 2
Beginning of life: 1600 watts
End of life: 1400 watts
Panels: 2 telescoping cylindrical solar panel with large area gallium arsenide solar cells
Batteries: 16-cell, 141 AH NiH
Solid apogee motor: Thiokol Star 30C
Stationkeeping thrusters N-S (bipropellant): 2 x 5.0 lbf
E-W (bipropellant) Fuel life: 2 x 5.0 lbf 12 Years
80" (2.03 m) diameter shaped surface reflector
Precision antenna pointing system maintains accuracy of better than 0.10 degrees Two shaped surfaces:
One for vertical linear polarization for communication
One for horizontal linear polarization for communications plus tracking
In orbit: H, deployed: 26 ft 2 in (7.97 m), W, deployed: 7 ft 1 in (2.17 m)
Stowed: H: 10 ft 4 in (3.15 m), W: 7 ft 1 in (2.17 m)
Launch: 3186 lb (1445 kg)
In orbit (beginning of life): 1816 lb (824 kg)
Beacon Frequency: 10.701.250 Vertical
| About the Astra 2D Satellite
In August 1999, Hughes Space and Communications International, now Boeing Satellite Development Center, was awarded two satellite contracts from Société Européenne des Satellites (SES) of Luxembourg. The new awards are the 8th and 9th to Hughes from SES, and will bring the total number of satellites in the SES fleet to 13.
Astra 2D, the first spin-stabilized satellite in the SES fleet, is a Boeing 376HP, for high-power, satellite. It was successfully launched on an Ariane 5 on Dec. 19, 2000. The Boeing 376 is one of the most popular spacecraft models. The delivery-in-orbit contract includes the satellite, launch services, and ground station control software for use at the control center, plus training for new satellite controllers. The Astra satellites are controlled from the SES ground station at Betzdorf in Luxembourg.
Astra 2D is the 55th 376 to be ordered from Hughes and Boeing. It will carry 18 traveling-wave tube amplifiers, 16 of which will be active. The signals will be transmitted via 39-watt traveling-wave tube amplifiers. Astra 2D will deliver digital direct-to-home television to Great Britain and Ireland. Two of the satellite's four on-board receivers will be used at any given time.
The Boeing 376 spin-stabilized spacecraft consists of two main sections. One is the spinning section, which contains the apogee kick motor, power system, primary propulsion, and most of the attitude control and command and telemetry subsystem elements. The fully redundant subsystem controls and monitors the spacecraft through all mission phases. The primary propulsion subsystem controls spacecraft orbital velocity, inclination, attitude, and spin speed. The other main section of the spacecraft is the despun portion, which houses the customized communications payload, including the transmitters, receivers, and antennas. Astra 2D is similar to the other operational Boeing 376HP satellites, the first of which was launched in January 1996. A standard bus will be used.
All Boeing 376 models have two telescoping cylindrical solar panels. These panels and the deployable antennas are stowed for compactness during launch. The highly reliable design makes full use of a nickel-hydrogen battery to maintain uninterrupted broadcasting during eclipses. The Astra 2D solar panels use gallium arsenide solar cells similar to those proven on previous Hughes spacecraft. The 376 design minimizes the number of required mechanisms and has never had a deployment failure.
Boeing Satellite Development Center is the world's leading manufacturer of commercial communications satellites and a major provider of space systems, satellites and payloads for national defense, science and environmental applications.
| In Service
While active, most of Astra 2D's transponders were used to provide television channels available on the Sky Digital satellite service to the United Kingdom and Republic of Ireland and the non-subscription service, Freesat. Provision of rights-sensitive broadcasts Free to air was made possible by the satellite's beam that was tightly focused on the United Kingdom and Ireland. However, surrounding countries had the ability to pick up the signal (dependent on suitably sized satellite dishes) and so could still access Freesat from outside the UK. Some channels on 2D were encrypted with Videoguard (a proprietary encryption method by the NDS Group) and only Sky Digiboxes with valid cards could decrypt them.
The BBC broadcast all of its domestic television channels (including BBC HD and the regional variations) from the Astra 2D satellite, except the BBC News Channel and BBC Parliament which broadcast from Astra 2A. All domestic BBC channels have been free to air since 29 July 2003.
ITV also broadcast all its television channels (including regional variations of ITV1, and STV and UTV) from the Astra 2D satellite. All ITV channels have been free to air from 1 November 2005, although some regions reverted to Free-To-View encryption in 2008 when their lease on one 2D transponder could not be renewed.
Channel 4 broadcast most of its channels free to air from this satellite, including Channel 4, Channel 4+1, E4, More4 and Film4 along with their timeshift variants. All were unencrypted apart from the feeds of Channel 4, Channel 4+1, E4 and E4+1 intended for viewers in Ireland, which remain encrypted.
From November 2008, Five (now Channel 5), began to transmit free to air for the first time on Astra 2D, using borrowed space on a BBC transponders, allowing the channel to join Freesat.
End of Service
With a projected lifetime of 12 years, Astra 2D was expected to leave regular operational service towards the end of 2012 or the beginning of 2013 and so the Astra 1N satellite, designed for operation at Astra 19.2°E and launched in August 2011, was initially positioned at 28.2°E to temporarily replace Astra 2D until the start of service of its long-term replacement, Astra 2F, which was launched in September 2012.
Astra 1N started commercial service at 28.2°E in October 2011 with transponder testing in October and November. Channels on Astra 2D started to transfer to Astra 1N in December with Channel 5 (plus 5* and 5USA), the Channel 4 family and ITV channels all moving to the new satellite over the next two months. On February 24, 2012 the last remaining channels on Astra 2D (the BBC channels) switched off and started transmission from Astra 1N.
As of January 2013, Astra 2D remains in position at 28.2°E, though with no transponder activity.
| Astra 2D UK Spotbeam
The SES Astra 2D footprint only shows dish sizes for a very limited area.
This was a very conservative map, Astra 2D has been picked up as far south as the Canary Islands and Cyprus.
Large dishes were required for large areas of mainland Europe.
Even with large dishes, reception could be unreliable, depending on the time of day and weather conditions.
In some countries, there was quite a difference between horizontal and vertical transponders.
There seem to have been 'sidelobes', in some areas such as Sweden and Portugal and 'dead zones' such as souther Italy and Malta.
For more information, see Astra 2D Maps