The ConeXpress - Orbital Life Extension Vehicle (CX-OLEV) presents the operators of geostationary communications satellites ("comsats") with a pioneering opportunity to extend the revenue-earning life of their space assets by up to 10 years. |
|Orbital lifetime extension is of interest to comsat Clients whose satellites may be running low on propellant, or may be unable to perform attitude and orbit control due to onboard failures. CX-OLEV intercepts the Client's satellite in geostationary orbit, docks with it, and takes over its attitude and orbit control function. This is a seamless service which allows the Client to continue offering his communications services without interruption. || |
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The CX-OLEV programme is co-funded by ESA and Orbital Recovery Ltd (ORL). The project has successfully completed its feasibility studies and is about to embark on the design and development phase. The first launch is slated for 2008.
CX-OLEV combines the double function of Ariane 5 launcher payload adapter and stand-alone spacecraft. The CX-OLEV spacecraft has a conical shape with a base dimension of 2.6 m, a height of 0.9 m and a maximal mass of 1400 kg. The solar wing span is about 15 m. The CX-OLEV spacecraft makes a unique use of electric propulsion from the moment of orbital injection after launch (in GTO) until it docks with the Client satellite in GEO. The spacecraft is 3-axis stabilised and a cold gas propulsion system completes the electric propulsion for attitude control, rendezvous and docking operations. There is no chemical propulsion onboard.
Electric energy is supplied by high-efficiency Gallium Arsenide solar cells mounted on six deployable solar panels. Telemetry, telecommand and ranging functions are performed via two hemispherical S-band antennas which together form an omnidirectional radiation pattern.
|The onboard docking equipment consists of a capture tool that inserts a probe into the throat of the apogee motor of the Client satellite, locks itself to the throat by expanding the crown of the probe, and pulls the Client satellite back towards CX-OLEV by retracting the probe. The docking is consolidated with the aid of latching mechanisms. Undocking will be done in a reverse manner, after which the CX-OLEV can dock to a next Client S/C at a different location in the GEO arc. || |
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The first CX-OLEV will be developed along classic protoflight lines. The process involves building or purchasing mostly flight-worthy prototype units, assembling these on a structure, and exposing the resulting satellite to qualification test levels for durations that are shorter than those required in a full design qualification programme. Adopting a protoflight approach is justified on the basis that all the satellite equipment either exists off-the-shelf or draws on well-established technology. Subsequent satellites will be built to flight standard and will undergo more lenient so-called acceptance testing, primarily to flush out workmanship issues.
The greatest operational and design challenge relates to the docking with an uncooperative spacecraft by remote control in geostationary orbit. By 'uncooperative' is meant a satellite that has not been designed for docking, in contrast to most other docking missions where both spacecraft involved are equipped with purpose-built hardware and software. Commercial communications satellites fall into the uncooperative category, the more so as they wish to continue rendering their nominal services uninterrupted during docking. Fortunately, all comsats come equipped with apogee kick engines that are fired shortly after launch injection and are never used again. CX-OLEV docks to the comsat by attaching itself firmly to the nozzle of the inert apogee kick engine. Another challenge is for CX-OLEV to approach the Client comsat from a distance without losing sight of it, shadowing its solar panels, or colliding with it. This so-called rendezvous is achieved by equipping CX-OLEV with a sophisticated set of orbital, attitude and optical sensors in conjunction with onboard and ground processing power. The feasibility of the mission and the attendant spacecraft design has been demonstrated to the satisfaction of ESA and ORL.
Following docking, CX-OLEV will perform the following services for a Client spacecraft weighing up to 2500 kg:
CX-OLEV is capable of multiple dockings and undockings, and is therefore ideally suited for the orbital management of individual spacecraft as well as satellite fleets.
- high-precision attitude control
- north-south and east-west station-keeping
- inclination reduction and node rotation
- relocation along the geostationary orbit arc
- removal from the geostationary orbit to a disposal orbit.
The ConeXpress-Orbital Life Extension Vehicle (CX-OLEV) is a S/C for on-orbit servicing of fuel depleted GEO comsat and is based on the ConeXpress platform as developed under ESA/telecom by a European industrial team led by Dutch Space. The phase B1 as executed during 2004 has been succesfully closed with a baseline review by ESA and Orbital Recovery Ltd. Feasibility of CX-OLEV and the mission has been demonstrated and a baseline design has been established as well as the programmatics for the implementation phase. The first part of this implementation phase, a B2 phase ending with a Preliminary Design Review is envisaged to start April 2005.
Last Update: 22 Nov 2010