Galileo-IOV PFM (Thijs)

Spacecraft nº:

ESA spacecraft nº: 74

Launch data: Designation  37846 / 11060A Launch date  21 Oct 2011 - 10:30 UT Launch site  Ko, ELS Launch vehicle  Soyuz-2-1B Fregat-MT Mission  Commercial: Navigation MEO Earth orbit: Perigee / Apogee  23240 x 23306 km Eccentricity  1,11E-03 Inclination  54.68 deg Period  846.88 min

Spacecraft data:

Description:

• GALILEO-PFM is a navigation satellite part of the European Union's Galileo program.
• The Galileo satellite navigation system will consist of a total of 30 spacecraft in three planes in medium Earth orbit, which will each be occupied by nine satellites, and with three spares satellites distributed on the three orbital planes. At an altitude of 23,616 kilometers and an inclination of 56 degrees, the system will provide accurate positioning data to users as far north as 75 degrees longitude.

• The L-band antenna transmits the navigation signals in the 1200-1600 MHz frequency range.
• The SAR (Search and Rescue) antenna picks up distress signals from beacons on Earth and transmits them to a ground station for forwarding to local rescue services.
• The C-band antenna receives signals containing mission data from Galileo Uplink Stations. This includes data to synchronies the on-board clocks with a ground-based reference clock and integrity data which contains information about how well each satellite is functioning. The integrity information is incorporated into the navigation signal for transmission to users.
• Two S-band antennas are part of the telemetry, tracking and command subsystem. They transmit housekeeping data about the payload and spacecraft to ground control and, in turn, receive commands to control the spacecraft and operate the payload. The S-band antennas also receive, process and transmit ranging signals that measure the satellite’s altitude to within a few meters.
• The infrared Earth sensors and the Sun sensors both help to keep the spacecraft pointing at the Earth. The infrared Earth sensors do this by detecting the contrast between the cold of deep space and the heat of the Earth’s atmosphere. The Sun sensors are visible light detectors which measure angles between their mounting base and incident sunlight.
• The laser retro-reflector allows measurement of the satellite’s altitude to within a few centimeters by reflecting a laser beam transmitted by a ground station. The laser retro-reflector is used only about once a year, as altitude measurements via S-band antenna ranging signals are otherwise accurate enough.
• The space radiators are heat exchangers that radiate waste heat, produced by the units inside the spacecraft, to deep space and thus help to keep the units within their operational temperature range.

• A passive hydrogen maser clock is the master clock on board the spacecraft. It is an atomic clock which uses the ultra stable 1.4 GHz transition in a hydrogen atom to measure time to within 0.45 ns over 12 hours.
• A rubidium clock will be used should the maser clock fail. It is accurate to within 1.8 ns over 12 hours.
• The spacecraft has four clocks, two of each type. At any time, only one of each type is operating. Under normal conditions, the operating maser clock produces the reference frequency from which the navigation signal is generated. Should the maser clock fail, however, the operating rubidium clock will take over instantaneously and the two reserve clocks will start up. If the problem with the failed maser clock is unique to that clock, the second maser clock will take over from the rubidium clock after a few days when it is fully operational. The rubidium clock will then go on stand-by or reserve again. In this way, by having four clocks, the Galileo spacecraft is guaranteed to generate a navigation signal at all times.
• The clock monitoring and control unit provides the interface between the four clocks and the navigation signal generator unit (NSU). It passes the signal from the active master clock to the NSU and also ensures that the frequencies produced by the master clock and the active spare are in phase, so that the spare can take over instantly should the master clock fail.
• The navigation signal generator, frequency generator and up-conversion units are in charge of generating the navigation signals using input from the clock monitoring unit and the up-linked navigation and integrity data from the C-band antenna. The navigation signals are converted to L-band for broadcast to users.
• The remote terminal unit is the interface between all the payload units and the on-board computer.

Mission details:

• Europe's first two Galileo navigation satellites were launched on Oct 21, 2011. This was also the first Soyuz launch from the Centre Spatial Guyanais. The new Ensemble de Lancement Soyuz pad is a copy of the pads at Baykonur.
  The Soyuz ST-B launch vehicle is the Soyuz-2-1B variant; an uprated Fregat-MT upper stage was used for the first time.
• With orange flames spewing from 32 rocket engine nozzles, the 151-foot [46.0-m]-tall Soyuz 2-1b rocket swiftly rose from the launch pad in a rain shower at 1030 GMT (6:30 a.m. EDT; 7:30 a.m. local time).
• The kerosene-burning Soyuz jettisoned four strap-on boosters less than two minutes after liftoff, leaving the empty rockets to fall in the Atlantic Ocean. Flying with a modernized digital control system, the Soyuz core stage and third stage accelerated the rocket to nearly orbital velocity in approximately nine minutes.
• The rocket's Fregat-MT upper stage, modified to carry extra propellant, ignited for 13 minutes to propel the mission's payloads into an oval-shaped transfer orbit.
• The two satellites have been given the nicknames Thijs and Natalia after competition winners Thijs Paerlman (B - b. 2000) and Natalia Nikolaeva (b. 2002).