= Proba 2 =

= ESA Proba-2 =

'''Proba-2''', Proba stands for PRoject for OnBoard Autonomy. The Proba satellites are among the smallest spacecraft
ever to be flown by ESA, but they are making a big impact in the field of space technology. Proba-2 is the
second of the series, building on nearly eight years of successful Proba-1 experience.
= ABSTRACT =

Following on from the success of PROBA-1, which successfully completed its technological goals in its first
year of flight and continues to provide valuable scientific data now into its fifth operational year,
PROBA-2, now in phase C/D and due for launch in September 2007, will once again fly a suite of new
technology demonstrators with an ‘added value’ science package of four experiments. Altogether there are
seventeen new developments being flown on Proba-2, divided into two groups: platform technologies which
are part of the infrastructure and are mission critical and passenger technologies to gain flight heritage and
experience before committing them to the infrastructure of other missions. Of the four Science experiments, two
are dedicated to solar physics. The two other will study the space weather (plasma physics)
The paper will provide an overview of the PROBA-2 mission and spacecraft along with a description of the
scientific payload and technology experiments
= PROBA 2 MISSION SUMMARY =


ABSTRACT
Following on from the success of PROBA-1, which
successfully completed its technological goals in its first
year of flight and continues to provide valuable
scientific data now into its fifth operational year,
PROBA-2, now in phase C/D and due for launch in
September 2007, will once again fly a suite of new
technology demonstrators with an ‘added value’ science
package of four experiments. Altogether there are
seventeen new developments being flown on Proba-2,
divided into two groups: platform technologies which
are part of the infrastructure and are mission critical and
passenger technologies to gain flight heritage and
experience before committing them to the infrastructure
of other missions. Of the four Science experiments, two
are dedicated to solar physics. The two other will study
the space weather (plasma physics)
The paper will provide an overview of the PROBA-2
mission and spacecraft along with a description of the
scientific payload and technology experiments
=  PROBA 2 MISSION SUMMARY =

= 1.1. Mission objectives =

The PROBA 2 mission objectives, as deduced from the ESA requirements, can be summarized as follows:
 *   PROBA 2 will be a platform to demonstrate and validate new, advanced technologies in order to promote their usage in future missions,
 *   As such, PROBA 2 shall accommodate a number of selected technology experiments,
 *   PROBA 2 shall furthermore accommodate a series of scientific payloads, in the fields of space environment (plasma) and solar observations;
 *   The PROBA 2 system shall be designed to support an in-orbit operational lifetime of 2 years;
 *   The PROBA 2 orbit shall be preferably a LEO Sun-synchronous orbit with minimized eclipse time;
 *   PROBA 2 shall have a high degree of spacecraft autonomy and ground support automation.
= 1.2. Launch and orbit =

PROBA 2 is planned to be launched from Plesetsk, Russia, in September 2007, on a Rockot launcher.
PROBA 2 will be a secondary-passenger of the launch of the SMOS (ESA) spacecraft. It will be directly
injected in a Sun-synchronous LEO orbit, with an altitude between 700-800 km (baseline 728km) and
with the LTAN at 6:00 AM +/- 15 minutes. The orbit injection accuracy provided by the launcher is sufficient
to guarantee that the LTAN will remain within 6:00 AM +/- 45 minutes without the use of onboard propulsion.
The orbital period is approximately 100 minutes. The targeted orbit is eclipse-free for 9 months per year,
thus making the orbit well suited for the solar observing instruments. Maximum eclipse duration during the
eclipse season is less than 20 minutes. Since the orbit remains acceptable for the solar
observations during the complete mission lifetime, propulsion is not needed to support the mission.
However, as is documented below, a propulsion system is accommodated onboard PROBA 2 as a technology
demonstration.
= 1.3. Ground segment =

As for PROBA1, the PROBA2 spacecraft will be operated from the Redu Ground station (Belgium).
= PROBA 2 SPACE SEGMENT DESCRIPTION =

PROBA 2 has a weight of less than 130 kg and belongs to the class of the mini-satellites (Figure 1). Its
structure is built using aluminum and CFRP honeycomb panels. Triple junction Gallium Arsenide solar cells,
body mounted on 1 panel and mounted on 2 deployable panels, provide the power to the spacecraft and a Li-Ion
battery is used for energy storage. A battery-regulated, centrally switched 28V bus distributes the power to the
units and the instruments. A high performance computer, based on the LEON processor provides the
computing power to the platform and for instrument data processing. It accommodates the memory for
house-keeping data storage as well as a mass memory for the payload image data. The telecommunications
subsystem is designed to establish and maintain spaceground communications link with the ground segment
while the spacecraft remains sun-pointing. It is CCSDS compatible for up- and downlink in the S-band. The set
of ACNS units support Sun-pointing, inertial 3-axis attitude pointing as well as Earth pointing and a series
of attitude maneuvers. Furthermore, it performs all required navigation and maneuvering computations
onboard. The spacecraft platform provides full redundancy

= 2.1. PROBA 2 platform =
= 2.1.1. Mechanical and thermal =

The PROBA 2 structure is derived from the PROBA 1 structure and is compatible with launchers such as
ROCKOT, PSLV and DNEPR. The carrying part of the structure is composed of 3 aluminum honeycomb panels
mounted in an H-structure and a bottom board. Almost all units are mounted on these inner panels. The bottom
board acts as the interface with the launcher. All outer panels without solar cells mounted on them consist of
aluminum honeycomb panels as well. They are painted black/white according to the needs of the thermal
subsystem. The 2 deployable solar panels, as well as one outer panel with solar cells consist of honeycomb
panels with aluminum core and CFRP sheets. The sheets supporting the solar cells are covered with kapton
for electrical insulation. The deployable panels are permanently connected to the spacecraft body by hinges
based on Carpentier joints. The Carpentier joints  provide the opening torque at the moment of panel
release as well as the self-locking in the deployed position. During launch, the stowed panels are kept in
the stowed condition by the hold-down and release mechanism. This mechanism utilizes thermal knives to
release each panel by software command in orbit. 
= Providing flight opportunities =

The Proba satellites are part of ESA’s In orbit Technology Demonstration Programme: missions dedicated
to the demonstration of innovative technologies. In orbit demonstration is the last step on the technology
development ladder. New technology products need to be demonstrated in orbit, particularly when users
require evidence of flight heritage or when there is a high risk associated with use of the new technology.
In orbit demonstration is achieved through experiments on carriers of opportunity, e.g. the International
Space Station, or through dedicated small satellites such as the Proba series, which were created to increase
the availability of flight-testing opportunities.
= Ensuring a competitive European industry =

 
Small, low-cost missions allow small companies access to space and provide them with the experience that is essential for European industries to be competitive and innovative.
= Commitment to technological innovation =


Proba-2 is the result of ESA’s commitment to technological innovation. Altogether, 17 new technological developments and four scientific experiments are being flown on Proba-2. 
= Technology demonstrations =

 = '''The technology demonstrations are:''' =


 *  a new type of lithium-ion battery, developed by SAFT (FR)
 *  an advanced data and power management system, containing many new component technologies including the LEON processor developed by Verhaert Space (BE)
 *  combined carbon-fibre and aluminium structural panels, developed by Apco Technologies SA (CH)
 *  new models of reaction wheels from Dynacon (CA), startrackers from DTU (DK) and GPS receivers from DLR (DE)
 *  an upgraded telecommand system with a decoder largely implemented in software by STT- SystemTechnik GmbH (DE)
 *  a digital Sun-sensor, developed by TNO (NL)
 *  a dual-frequency GPS receiver, developed by Alcatel Espace (FR)
 *  a fibre-sensor system for monitoring temperatures and pressures around the satellite, developed by MPB Communications Inc. (CA)
 *  a new startracker development being test-flown before use on the BepiColombo mission, developed by Galileo Avionica (IT)
 *  a very high-precision flux-gate magnetometer, developed by DTU (DK)
 *  an experimental solar panel with a solar flux concentrator, developed by CSL (BE)
 *  a xenon gas propulsion system using resistojet thrusters and a solid-state nitrogen gas generator to pressurise the propellant tanks, developed by SSTL (GB) and Bradford (NL)
 *  an exploration micro-camera (X-CAM), developed by Micro-cameras & Space Exploration (CH)
 *  new GNC algorithms developed by NGC (CA) 
= '''The two solar observation experiments are:''' =


 *  a Large Yield Radiometer (LYRA) that will monitor four bands in a very wide ultraviolet spectrum, with Centre Spatial de Liège as lead institute supported by the Royal Observatory of Belgium as scientific leader and with an international team comprising PMOD (CH), IMOMEC (BE) and BISA (BE)
 *  an extreme-ultraviolet telescope (SWAP) using new pixel sensor technology (APS), that will make measurements of the solar corona in a very narrow band, with Centre Spatial de Liège as lead institute supported by the Royal Observatory of Belgium and with an industrial team comprising Alcatel-Lucent (BE), AMOS SA (BE), DELTATEC (BE), Fill
Factory NV (BE) and OIP NV (BE) 
= '''The two space weather experiments are:''' =


 *  Dual Segmented Langmuir Probes (DSLP), which will measure electron density and temperature in the background plasma of the Earth’s magnetosphere
 *  a thermal plasma measurement unit (TPMU), that will measure ion densities and composition 

Both were developed by a Czech consortium, led by the Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic (CZ).

In total, ten European countries and Canada were involved in the construction of the Proba-2 satellite.
= Effective Engineering =

 
To ensure on board autonomy, mission control system development is an integral part of the overall mission programme, along with the associated operations. Development occurs incrementally, with progressive validation taking place throughout activities ranging from software development, spacecraft integration and system testing to in-orbit operations.

=  =External links==

{{Official Page|[http://www.esa.int/esaMI/Proba/SEMJJ5ZVNUF_0.html]}}
{{Factsheet|[http://esamultimedia.esa.int/docs/Proba/Proba-2_Factsheet_8oct.pdf]}}