Artemis ready for launch this summer

ESA’s newest communication satellite Artemis
(Advance Relay and TEchnology MISsion) has undergone its final testing at ESA’s Technology centre ESTEC in Noordwijk the Netherlands.
Originally the satellite was scheduled to be shipped to Tanegashima space centre
in Japan last October, for its launch by a Japanese H-IIA rocket
on February 01, 2001. But problems with that launcher kept Artemis
in Europe several extra months. In March Artemis
left ESTEC for this summer’s launch by an Ariane-5 rocket.

The European Space Agency (ESA) has an agreement with Japan’s space agency NADSA for use of the Artemis satellite. The co-operation between ESA and NASDA will give NASDA a 40% share of Artemis in-orbit data relay capacity, and ESA will get the free launch with the new H-IIA rocket. Problems with the H-IIA however resulted in a launcher change. NASDA made an announcement on September 26, 2000 [1], to launch the fist H-IIA just to test its performance and not launch Artemis. After that announcement it was unclear what would happen with Artemis, but a launch with Europe’s own Ariane-5 was the most likely. “An Ariane-5 launch has the least impact on getting the satellite ready for launch before the end of 2001”, according to the Artemis project manager Leo van Holtz. He continues; “Artemis was originally built for launch on an Ariane-5. The environmental levels of Ariane-5 and H-IIA are the same so there are no major design changes needed to the satellite, so we can still launch in 2001”. On February 15 it was made official by both ESA and Arianespace to launch Artemis on an Ariane-5 launcher sometime between June and August 2001. The launch contract was signed at ESA Headquarters in Paris by Antonio Rodotà, Director General of ESA, and Jean-Marie Luton, CEO of Arianespace. [2]. "By signing this contract a few months before the launch, Arianespace once again demonstrates its responsiveness and flexibility in meeting customer requirements,” Jean-Marie Luton said. [3]. The Artemis satellite and its support equipment left ESTEC on March 05, for a three week trip to Kourou, French Guiana. The launch campaign in Kourou will start at the beginning of April and the satellite will be ready for launch by early June.

The Artemis satellite

The 800 million Euro project-contract to built Artemis was awarded by ESA to a consortium of companies led by Alenia Aerospazio of Italy. Artemis has a height of 4.5 meters and a length of 24.7 meters. The launch mass of the satellite will be 3.1 tons. Ones in orbit, 36.000 km above the Earth, at a position of 21.5 degrees East, Artemis can be in constant communication with satellites in Low-Earth Orbit (LEO) for long periods of each orbit, and can beam the data from those satellites directly to the end user on the ground in Europe and North Africa.

Artemis is a satellite for testing and operating new telecommunications services. Communications is one sector of space activity that has a truly commercial nature. The Artemis spacecraft will herald the start of a new generation of technology and communications services. Artemis is not the conventional type of communication satellite. In particular it differs in one very important aspect: none of its payloads connects a fixed point on the Earth with other fixed points on the Earth. Instead:

* Artemis will connect users on the ground with satellites in orbit via its radio frequency data relay payload. This dramatically increases communication time with spacecraft in low-Earth orbit.

* With Artemis, a mobile user will be able to link up from anywhere in Europe, North Africa or the Middle East to any fixed user in the same area at very competitive prices. Large ocean areas are included in Artemis’ coverage zone, allowing voice or data connections to land from the Mediterranean, the North Sea or the eastern part of the Atlantic Ocean.

*The navigation payload will enable users to determine their position with higher accuracy and 24-hour availability. Artemis will add corrections and health checks to the existing GPS signals, thus supporting the first phase of Galileo, Europe’s new navigation programme.

*Via its optical data relay payload, SILEX, Artemis can receive and re-transmit in real time.

SILEX

The laser communications terminal aboard Artemis, known as SILEX (Semiconductor Laser Inter-satellite Link Experiment) is the worlds first inter-satellite communications data relay system using lasers as carriers for the signal transmission. There are two SILEX terminals built, one of them was launched on the French SPOT-4 satellite in 1998, the other will fly with Artemis. With Artemis in orbit the two terminals will transmit the image data of the SPOT-4 at a rate of 50 megabits per second (Mbps) to the ground station near Toulouse. In addition to this data transmission, SILEX will also support an experiment between OICETS (Optical Inter-orbit Communications Engineering Test Satellite), a Japanese satellite due for launch also in 2001, and Artemis. During this experiment the data rate from OICETS to Artemis will be 50 Mbps, but there will be an optical link between the two satellites also. Via this optical link a data stream of 2 Mbps can be sent from the ground to OICETS via Artemis. The advantage of SILEX is very high data rates, less power consumption and interference, and a saving of weight compared to conventional radio beam terminals.

ION propulsion Subsystem (IPS)

Artemis will be the first ESA satellite to fly with electric propulsion technology operationally. It will be used for inclination control during the 10-year lifetime of Artemis. The IPS consists of two thruster assemblies one on the north and one on the south side of the satellite. Each assembly comprises an Ion Thruster Alignment Mechanism upon which two redundant thrusters are mounted, a Radio-frequency Ion Thruster (RIT) and an Electro-bombardment Ion Thruster (EIT). Each of these thrusters has its own control equipment and power supply and also its own flow control/propellant monitoring units. Xenon is the propellant used; 40 kg are loaded on board Artemis. If they didn’t use IPS, the propellant needed would be 400 Kg. So it is a big weight saver. When the IPS is working it needs about 600 W power, which comes directly from the solar arrays and later in life from the onboard batteries.

Satellite users

As mentioned above, Japan will use 40 % of the Artemis satellite. The OICETS, and Adeos-II, satellites will transmit data via Artemis. Also the Japanese JEM Module of the International Space Station will use Artemis to give scientist a chance to monitor the status of experiments that astronauts perform in on board the station in real time and it gives them an opportunity to actively intervene. The European Envisat and SPOT-4 as well as the Italian David satellites will also transmit data via Artemis.

Thanks to: Leo van Holtz (Artemis project manager) and Heidi Graf (ESTEC Public Relations)

Notes:

[1] AFP news release, September 26, 2000

[2] ESA press release (09.01) February 15, 2001

[3] Arianespace press release, February 15, 2001