OPS1 building

Main Equipment Room (MER)

 



MARECS Baseband System and C-Band Control Terminal Console

This terminal console is used to monitor and control all subsystems of MARECS C-band terminal. MARECS-B2 is a geosynchronous satellite used, at present, to provide differential GPS data of  Africa and South America. This data is decoded by South American and African users' GPS receivers obtaining a position acuracy within 1 meter.

From this console, the operator can monitor the status of all the units located in MARECS C-Band antenna. They can also select the redundant uplink / downlink front-end chains and move the C-Band antenna from remote servo unit.... A visual and audible alarm will be generated in case of any abnormal status of any unit installed in MARECS C-Band Apex cabin or in MER MARECS systems.

The racks located behind this console house MARECS Telemetry, Telecommand, Ranging and Monitor & Control systems.




VIL2 Baseband System and VIL2  Control Terminal console

These racks house the following subystems:

Telemetry subsystem

RF signal  coming from the spacecraft is amplified and downconverted in VIL2 antenna.Then ISO received signal is demodulated, reconstructed, formatted and sent to ISO computer room for further processing.

Telecommand subsystem

Telecommands can be originated from either ISO computer OCC, ESOC/MSSS (when supporting any other scheduled satellite) or locally from the STC in its telecommand back-up configuration. All commands are acknowledged and checked and sent to VIL2 antenna where they are amplified and sent to the spacecraft.

Ranging subsystem

It is Multi-Purpose Tracking System (MPTS) type. It provides ranging and/or integrated Doppler data and can be used in three modes for the support of: With a coherent transponder the basic measurement is one of integrated Doppler shift, which, by itself allows orbit determination. The measured Doppler shift on the received carrier can also be used for an accurate prediction of the returned range tone frequency. This allows the use of a very narrow phase lock loop (PLL) to recover the range tone from the noise. To achieve this, it is necessary that all the station local oscillators for both up and down link chains are coherent with the same frequency reference. In this case the carrier and the ranging tone frequency are affected by the two-way Doppler shift produced by the relative motion between the ground station and the spacecraft.

The measurement of (2-way) range is made by determination of the time elapsed between the instant at which a known code sequence is transmitted ant the instant at which it is received, using the spacecraft transponder as an active repeater. Codes of sequentially increasing length are used in order to reduce the time required for the synchronization of the received code. The sequence used is periodic, in order to permit repetitive measurements and it contains a high frequency tone phase modulated by a sub-harmonically coherent code. The propagation delay is measured using a time counter periodically started by the first chip of the transmitted code and stopped by the first chip of the replica code synchronous with the received one.

Monitor and control subsystem

Monitor and Control of the VIL2 terminal is carried out via the Station Computer (STC) by means of the Advanced Monitor and Control Module (AMCM) located in the Main Equipment room (MER) and the FEC located in the antenna equipment room.

The AMCM takes care of the monitoring and setting-up of all VIL2 units installed in MER.

The Mark III FEC automatically performs front end equipment control functions, spacecraft acquisition and tracking scheduled operations. It is in charge of monitoring and controlling all front-end units, reporting and logging any event and of generating pointing data.

Station computer

The STC is a general purpose computer provided in all ground stations. It interfaces to AMCM, FEC and VILSPA comms node. Therefore its services are available to remote users. Its main functions are local / remote monitoring and local / remote control of all VIL2 units.

The operator selects the desired control command name and the STC sends the command to the device. The control command can initiate JOBS which are integrated sequences of commands arranged to carry out pre-defined configuration and test activities.
 



VIL2 Control Terminal Console

VIL2 terminal is monitored and controlled from this console. It houses several TS1 and VIL2 units (from left to right):

TS1 station computer remote Pan display and its control keyboard.

MER operator can monitor and control TS1 from this position (see 'TS1 TT&C Terminal' description). Single or macro-commands can be sent from this control keyboard to any of the TS1 devices which is under station computer control. Parameters status of each device can be displayed in this monitor by selecting its appropriate page/s. All parameters are displayed in different colours: green (nominal), red (alarm), blue (device connection to STC lost), yellow (an acknowledged known alarm)......

Several support functions can also be performed from this position:

VIL2 station computer Pan display and its control keyboard.

Similar functions as the ones explained in 'TS1 station computer remote Pan display...' paragraph, with the exception that:
- VIL2 macro-commands, called JOBS, are macros of macro-commands (lot of configuration tables have to be loaded in some VIL2 units).
- Local rangings results can be retrieved from MPTS disk by Flight Dynamics department.
- Telemetry recording and playback is not possible from TFP's in Mark III mode.
 

Portable Spacecraft Simulator (PSS)

This PC-based PSS generates spacecraft simulated data to be used for testing VIL2 downlink facilities. PSS output modulates an RF signal that after appropriate up-conversion can be sent to an antenna probe located in VIL2 subreflector. A station validation readiness check can be performed by the corresponding spacecraft controller by monitoring this simulated data prior each satellite acquisition.


 

MARECS and ECS Frequency & Timing system
The frequency part of the system consists of a rubidium frequency standard.Its 5 MHz output pilots two stable quartz frequency standards whose 5 MHz output is injected into an automatic frequency switching module (FSM) that will switch over to the backup quartz standard in the event of a failure of the prime standard. The 5 MHz, 1 MHz and 100 kHz outputs of the FSM are fed to two identical frequency distribution amplifiers. Their mission is to provide frequency outputs of 5 MHz, 1 MHz and 100 kHz to pilot all  ECS and MARECS devices with oscillators, capable of being piloted with an external reference signal with the frequency accuracy of the rubidium oscillator 5 MHz output ( 5 x 10-11 ).

The timing part consists of three Time Code Generators (TCG) which are piloted by 1 MHz from the frequency distribution amplifiers. Timing data, 1 PPS reference and monitoring status of each of these 3 units is sent to a Majority Decision Unit (MDU). In case of failure of one TCG, MDU will output the time of the majority (2 good, 1 faulty). Available time codes are IRIG-B, SLOW and BINARY (Julian time).

1 PPS output (1 second) of MDU is being compared continuously with 1 second reference from one GPS receiver installed in VIL2 Frequency & Timing racks. Periodical adjustment corrections are performed to rubidium standard in order to keep timing station within a ±30 µs window.

A similar Frequency an Timing System in integrated in VIL2 Terminal. The main differences between the one just described and the one installed in VIL2 Terminal are:


ECS Ranging Baseband System

Ranging operations are performed daily to ECS-4 and ECS-5 satellites. Ranging request are initiated by the ECS spacecraft controller (located at Redu TT&C station) and the results are sent automatically to Redu.
It is a LCT Tone Ranging System type (TRS). The TRS phase modulates a 70 MHz carrier with a 100 KHz sine wave, called major tone. LCT output is sent to ECS Ku-band front-end located at PTL room where is upconverted to 14.125 GHz, amplified and uplinked to the spacecraft. The received transponded signal is is applied to the ranging demodulator which phase locks on the transponder tone. The received tone is then compared in phase with the transmitted tone. The phase difference between the two tones is proportional to the range station-satellite-station.
The above measurement has an intrinsic ambiguity to be solved. This is done by transmitting minor tones sequentially (20, 16.8, 16.16, 16.032 and 16.008 KHz) to the spacecraft. Only after ambiguity resolution, valid ranging data are obtained.


GPS TDAF System

A pilot GPS Tracking and Data Analysis Facility (TDAF) is currently in operation which comprises a control centre located at ESOC and six remote stations, one of which is located at VILSPA. All of them are remotely control from ESOC. The GPS-TDAF system is designed to achieve high accuracy orbit determination and to perform error analysis for future spacecraft missions.
 


GPS receiver and GPS terminal

GPS TurboRogue receiver

It was jointly developed by Allen Osborne Associates and the Jet Propulsion Laboratory (JPL) in order to provide high accuracy digital processing of GPS satellite signals received thru a GPS antenna located 150 meters away from this rack.
The receiver tracks up to eight (twelve optionally) satellites simultaneously while measuring the group delays (pseudorange) and phase delays. Its hardware and software employ unique signal processing techniques to extract accurate group delays which exhibit sub-centimetre level systematic errors (excluding antenna and multipath errors) when two or more satellite measurements are differenced. Phase measurements also provide a high degree (sub-millimetre) of accuracy and precision.

GPS terminal

It is a PC which provides communications support and remote operation capabilities between GPS receiver and GDAF control centre (a SUN workstation located at ESOC). Communications for remote operations and data retrieval is via a PAD connection. The GPS receiver generates data which produces a compressed data file of around 600 Kbytes every day and this is transferred to ESOC every twenty four hours.

 
Payload Test Laboratory (PTL) room



ECS Fluxmeter & Ranging Front-end

It is used for the following functions: The Fluxmeter system is designed to measure any PFD in the range -114 to -167 dBW/m2. During OTS-2 life, a radiometer consisting of a 1.5m dish, a rain gauge and a temperature gauge were installed. Its function was to measure the antenna noise temperature and therefore the atmospheric attenuation in the frequency range 11 GHz to 12 GHz.

Received PFD, antenna noise temperature, ambient temperature and instantaneous value of the rainfall were recorded in two strip chart recorders 24 hours/ day, 7 days / week. Thus, annual absolute and relative PFD at Ku-band frequencies in Southern Europe were registered and evaluated for future telecommunications satellites design.



MARECS-B2 Payload Test Laboratory

As explained in Villafranca main projects , MARECS Shore to Ship link (Forward Link) through the satellite is established at C-band for the up-path and at L-band for the down-path. The Ship to Shore Link (Return Link) is performed at L-band for the up-path and at C-band for the down-path.

MARECS PTL facilities were provided in order to measure and monitor the payload performance of MARECS-A and MARECS-B2 throughout their satellite mission. For this, a C-band front-end similar to any PTT station that communicates with ships and one L-band terminal similar to the one installed in a ship were required.

At present, it is used to monitor L-Band FUGRO return signal from MARECS spacecraft.





COMMS room





Meeting room

OPS1 meeting room is either used for training courses, lectures or working meetings. A VHS video tape recorder and a TV monitor is available for showing to visitors the activities performed by ESA and VILSPA. It is also provided with an NTS video-conference system connected to 3 ISDN BRI.

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