ESA Science & Technology - Publication Archive

SMART-1 is the first of the Small Missions for Advanced Research in Technology of the ESA Horizons 2000 scientific programme. The SMART-1 mission is dedicated to testing of new technologies for future cornerstone missions, using Solar-Electric Primary Propulsion (SEPP) in Deep Space. The chosen mission planetary target is the Moon. The target orbit will be polar with the pericentre close to the South-Pole. The pericentre altitude lies between 300 and 2000km, while the apocentre will extend to about 10,000km. During the cruise phase, before reaching the Moon, the spacecraft thrusting profile allows extended periods for cruise science. The SMART-1 spacecraft will be launched in the spring of 2003 as an auxiliary passenger on an Ariane 5 and placed into a Geostationary Transfer Orbit (GTO). The expected launch mass is about 370kg, including 19kg of payload. The selected type of SEPP is a Hall-effect thruster called PPS-1350. The thruster is used to spiral out of the GTO and for all orbit maneuvers including lunar capture and descent. The trajectory has been optimised by inserting coast arcs and the presence of the Moon's gravitational field is exploited in multiple weak gravity assists. The Development Phase started in October 1999 and is expected to be concluded by a Flight Acceptance Review in January 2003. The short development time for this high technology spacecraft requires a concerted effort by industry, science institutes and ESA centres. This paper describes the mission and the project development status both from a technical and programmatic standpoint.

Presentation from the press event marking the beginning of Cluster's operational phase - held at ESA HQ, 16 February 2001.

Presentation from the press event marking the beginning of Cluster's operational phase - held at ESA HQ, 16 February 2001.

Presentation from the press event marking the beginning of Cluster's operational phase - held at ESA HQ, 16 February 2001.

Presentation from the press event marking the beginning of Cluster's operational phase - held at ESA HQ, 16 February 2001.

In keeping with ISO's role as an observatory, the majority of its observing time will be available to the astronomical community. The traditional route of Calls for Observing Proposals, followed by peer review, is being used. There has been one Call prior to launch and a single Supplemental Call is foreseen post-launch. The expected high sensitivity of the ISO instruments will lead to observations of relatively short duration, typically tens of minutes to a few hours. This, in turn, means that many thousands of observations using the four highly sophisticated instruments with multiple operating modes will be carried out in ISO's limited lifetime of 18 months. Thus, as many as possible of the processes, from proposal submission to sending specific commands to the satellite to carry out a particular observation, have been automated. In addition, all details of the desired observations have to be specified by the observer in advance of the observation being executed to allow the complex observing programmes to be established.

ISO, the Infrared Space Observatory, will provide astronomer's with an unprecedented opportunity - and the only one for the next 10 years - to make scientific observations of weak infrared radiation sources. The development of the Observatory proved to be a challenging task: there was little available experience with the advanced technologies required for such a new infrared-astronomy mission. The scientific instruments were developed by groups of scientific institutes and industry under national funding. The satellite was developed, manufactured, integrated and tested by an industrial consortium made up of 32 companies, mostly from Europe. ESA is performing the flight operations. The USA and Japan are also contributing to the mission in return for observation time.

he payload of ESA's Infrared Space Observatory (ISO) consists of four scientific instruments: a camera (ISOCAM), an imaging photo-polarimeter (ISOPHOT), a long-wavelength spectrometer (LWS), and a short-wavelength spectrometer (SWS). Each of these instruments was built by an international consortium of scientific institutes using national funding. ESA was responsible for their subsequent integration into the ISO spacecraft and will carry out the in-orbit operations.

ESA's Infrared Space Observatory (ISO) consists of two modules: the Payload module, which includes the telescope and the scientific instruments, and the Service Module, which houses the instruments electronics, the hydrazine propellant tank and all other classical spacecraft subsystems. To ensure that the telescope is kept near absolute zero and thus is the least disturbed by the effects of the infrared emissions from other elements of the system, the telescope is enclosed in a helium-cooled cryostat. The cryostat in turn is shaded by a Sun-shield to protect it from the heat of the direct Sun. The shield has a covering of solar cells that provide the electrical power needed for the mission.

The Infrared Space Observatory (ISO) satellite will be the world's first true astronomical observatory in space operating at infrared wavelengths. Astronomers will be able to choose specific targets in the sky and point ISO towards them for up to ten hours at a time to make observations with versatile instruments of unprecedented sensitivity. During its lifetime of 18 months, ISO will be used to observe all classes of astronomical objects ranging from planets and comets in our own solar system, right out to the most distant galaxies.

The roots of the SOHO mission and the story leading to the comprehensive observatory that the spacecraft is today are summarised here. Now fully operational in its halo orbit around the first Lagrangian point (L1) between the Earth and the Sun, SOHO is providing the international scientific community with the unique opportunity, and also challenge, of understanding the Sun and heliosphere as one complex, global system. It is a superb tool with which to investigate our daylight star and its circumstellar environment, from the Sun's centre, through its visible surface and tenuous corona, and out into the heliosphere to distances corresponding to more than ten times the orbital distance of the Earth.

ESA's Infrared Space Observatory (ISO) was successfully launched from the Guiana Space Centre in Kourou on 17 November 1995. Its requirements in terms of ground-segment preparation were particularly demanding due to the limited mission lifetime, which calls for highly efficient operations, the very fast pace of the ISO observations, some lasting just a few minutes, the severe pointing requirements which demand sophisticated planning, and the real-time commanding of the highly sophisticated payload of four instruments with multiple operating modes from a computer- generated, automatically executing file. It was recognised that, given these demanding constraints, a well thought out approach to overall ground-segment integration, testing and validation would be required to ensure success. The approach that was chosen, based on the concept of end-to-end testing supported by sophisticated instrument simulators, proved highly effective. As a result, the ISO ground segment was ready to support all of the mission's operational phases in time for the spacecraft's launch.

This article gives a summary of the early in-orbit performance of the Agency's recently launched Infrared Space Observatory (ISO) spacecraft and its instruments and presents some of the initial scientific results.

The Cluster mission will be operated from ESOC. In addition to the mission challenges imposed by the simultaneous operation of four co-ordinated spacecraft, ESOC will be responsible for maintaining the software of the On-Board Data Handling (OBDH) subsystem from the time of launch until the end of the mission, which is nominally two and a half years. This on-board software maintenance capability provides a powerful means of adapting the behaviours of the four Cluster spacecraft to the real-time status of the hardware of each and to any operational difficulties that they might encounter during their operating lifetimes.

The Cluster mission is designed to study the small-scale structures that are believed to be fundamental in determining the key interaction processes in cosmic plasma. The mission will be controlled from ESOC, which will also be responsible for commanding the scientific payloads of the four spacecraft, in collaboration with the Cluster Principal Investigators (PIs), and for collecting and distributing the mission results to the scientific community. To support the Cluster mission operations, ESOC has developed the Cluster Data Processing System (CDPS), the architecture of which is based on three main components.

The Cluster mission was first proposed to the Agency in late 1982 and was subsequently selected, together with SOHO, as the Solar Terrestrial Science Programme (STSP), the first Cornerstone of ESA's Horizon 2000 Programme. This article gives an overview of the complex chain of events that have taken place between the loss of the original mission with the Ariane-5 launch failure and the recent approval of the recovery mission known as Cluster-II.

Huygens is being carried as a passenger on NASA's Cassini Orbiter to Saturn, where it will be released to enter the atmosphere of Titan, the planet's largest moon. During the controlled descent phase, its instruments will execute a complex sequence of measurements to study the atmosphere's chemical and physical properties and, if it survives impact, Huygens will collect data on Titan's surface properties. Flight operations will be conducted from the Huygens Probe Operations Centre (HPOC) at ESOC. This article describes the ground-system infrastructure, procedures and constraints involved in operating Huygens over its 6.7-year mission lifetime.

Many engineering challenges had to be overcome in designing the first probe planned to study a moon beyond the Earth's system. An extensive development programme was undertaken, involving several unusual tests, driven by the mission's unique aspects. ESA's Huygens Probe will be delivered to Titan, Saturn's largest satellite, by the Cassini Orbiter in 2004. After a dormant interplanetary journey of 6.7 years - although Huygens will be activated every 6 months for health checks - its aeroshell will decelerate it in less than 3 min from the entry speed of 6 kms^-1 to 400 ms^-1 (Mach 1.5) by about 160 km altitude. From that point, a pre-programmed sequence will trigger parachute deployment and heat-shield ejection. The main scientific mission can then begin, lasting for the whole of the Probe's 2-2.5 h descent.

The Huygens Probe is ESA's element of the joint Cassini/Huygens mission with NASA to the Saturnian system. Huygens will be carried on NASA's Cassini Orbiter to Saturn, where it will be released to enter the atmosphere of Titan, the planet's largest satellite. The Probe's primary scientific phase occurs during the 2-2.5 h parachute descent, when the six onboard instruments execute a complex series of measurements to study the atmosphere's chemical and physical properties. Measurements will also be conducted during the 3 min entry phase, and possibly on Titan's surface if Huygens survives impact. This article provides an overview of the mission and a concise description of the payload.

Direct evidence of the constitution of cometary volatiles is particularly difficult to obtain, as the constituents observable from Earth and even during the flybys of Comet Halley in 1986, result from physico-chemical processes such as sublimation and interactions with solar radiation and the solar wind. What we know today about cometary material from those earlier missions and ground-based observations does, however, demonstrate the low degree of evolution of cometary material and hence its tremendous potential for providing us with unique information about the make up and early evolution of the solar nebula.