ESA Science & Technology - Publication Archive

Following launch and its 5-month interplanetary cruise, Venus Express was injected into a 24 h orbit around Venus. It is now conducting science observations for two Venusian days (486 Earth-days). This paper describes the ground system infrastructure, the orbital requirements and mission control parameters, the flight operations concept, principles and implementation for the various mission phases and payload operations, and the mission products to be made available to the scientific community.

The success of a scientific mission is determined by the quality of the scientific results. The prompt delivery of instrument and ancillary raw data to the instrument teams and the delivery of reduced and calibrated data to the scientific community are therefore key elements in the mission design. This paper describes the data flow from the Venus Express spacecraft through the ground segment via the instrument teams to the final scientific archive. Several software tools and standards are used to support the data dissemination. The functionality of the individual tools is explained, the interfaces to the individual groups are discussed and examples of the graphical user interfaces are shown.

The general objective of ASPERA-4 (Analyser of Space Plasmas and Energetic Atoms) is to study the solar wind-atmosphere interaction and characterise the plasma and neutral gas environment in near-Venus space through energetic neutral atom (ENA) imaging and local charged particle measurements. The studies address the fundamental question: how strongly do the interplanetary plasma and electromagnetic fields affect the atmosphere of Venus? ASPERA-4 comprises four sensors: two ENA sensors, and electron and ion spectrometers. The Neutral Particle Imager (NPI) measures the integral ENA flux (0.1-60 keV) with no mass or energy resolution but relatively high angular resolution. The Neutral Particle Detector (NPD) measures the ENA flux, resolving velocity (0.1-10 keV for hydrogen) and mass (H and O) with a coarse angular resolution. The electron spectrometer (ELS) is a standard top-hat electrostatic analyser (energy range 0.001-20 keV) in a very compact design. These three sensors are on a scanning platform providing 4p coverage. ASPERA-4 also contains an ion mass composition sensor, IMA (Ion Mass Analyser). Mechanically, IMA is a separate unit electrically connected to the ASPERA-4 main unit. IMA provides ion measurements in the energy range 0.01-36 keV/q for the main ion components H⁺, He⁺⁺, He⁺, O⁺⁺, O⁺ and CO⁺₂ ion group with M/q > 40 amu/q.

Venus Express was launched in late October, 2005, and arrived at the planet in April 2006, where it is now in orbit and the return to Earth of new information about Venus' atmosphere, surface, and space environment has begun. The purpose of this special issue of Planetary and Space Science is to lay out the background to the mission, in terms of the planet and its mysteries as well as the spacecraft, its instruments, and the planned observations, in order to review the context in which the new results will be analysed and interpreted.

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Of all the non-terrestrial ionospheres and thermospheres in our solar system those of Venus have been explored and studied the most. This is mainly because of the 14 year exploration of the well instrumented Pioneer Venus spacecraft and the theoretical studies prompted by the resulting observational information. However, there are still a number of important scientific questions that remain unanswered. These include: i) dynamics of the thermosphere; ii) the energy mechanisms/sources responsible for maintaining the elevated plasma temperatures in the ionosphere; iii) airglow/aurora intensities and their sources; and iv) hot atom populations. Venus Express is likely to help address some of the issues listed under i), iii) and iv) above.

In the early morning of 9 November 2005, Venus Express left Earth aboard a Soyuz launch vehicle and headed for Venus. After several months of interplanetary cruise, a perfect capture burn on 11 April 2006 placed the spacecraft in orbit around our neighbouring planet. Only 48 hours later, the first astonishing images of the south pole were received on Earth. A few weeks later, after orbital manoeuvres, Venus Express achieved its operational science orbit ready to begin several years of observations.

At 07:17 UT (09:17 CEST) on 11 April 2006, the Venus Express spacecraft fired its main engine to enter orbit around Earth's sister planet, making ESA the first space agency to have vehicles orbiting the Moon, Mars and Venus at the same time. With this latest success, the Agency hasadded another celestial body to its range of targets in the Solar System. ESA is operating Mars Express around Mars and SMART-1 around the Moon, and is a partner on the Cassini orbiter circling Saturn. ESA also has the Rosetta spacecraft en route to Comet 67P/Churyumov-Gerasimenko.

This issue of the ESA Bulletin takes an in-depth look at the Venus Express mission. The successful launch, the mission, the spacecraft, the science return, as well as the ground segment and mission operations are featured.

In proceedings of the 4th International Spacecraft Propulsion Conference (ESA SP-555). 2-9 June, 2004, Chia Laguna (Cagliari), Sardinia, Italy. Editor: A.Wilson. Published on CDROM., p.88.1

ESA's ambition of inter-planetary exploration using a fast-track low cost industrial programme was well achieved with Mars Express. Reusing the platform architecture for the service module and specifically the Propulsion system enabled Venus Express to benefit from several lessons learnt from the Mars Express experience. Using all existing components qualified for previous programmes, many of them commercial telecommunication spacecraft programmes with components available from stock, an industrial organisation familiar from Mars Express was able to compress the schedule to make the November 2005 launch window a realistic target. While initial inspection of the CPS schematic indicates a modified Eurostar type architecture, - a similar system using some Eurostar components - would be a fairer description. The use of many parts of the system on arrival at the destination (Mars or Venus in this case) is a departure from the usual mode of operation, where many components are used during the initial few weeks of GTO or GEO. The system modifications over the basic Eurostar system have catered for this in terms of reliability contingencies by replacing components, or providing different levels of test capability or isolation in flight. This paper aims to provide an introduction to the system, address the evolution from Eurostar, and provide an initial assessment of the success of these modifications using the Mars Express experience, and how measures have been adopted specifically for Venus Express.

In proceedings of the 4th International Spacecraft Propulsion Conference (ESA SP-555), 2-9 June, 2004, Chia Laguna (Cagliari), Sardinia, Italy. Editor: A.Wilson. Published on CDROM., p.115.1

An insufficient amount of pressurant gas in the propulsion system or a working temperature in the pressurant tank outside the qualification limits can cause a decrease in the performance of the thrusters or even the loss of the mission. This paper presents an engineering tool used able to compute the Pressurant budget of a mission and the effects of influencing parameters. The updated tool allows to also compute the temperature, pressure and mass evolution inside the pressurant tank during the various mission phases. The tool has been used to verify the calculations done by Astrium Stevenage for Mars Express and Venus Express. The pressurant gas used for both cases was helium. The tool permits to use other combinations of pressurant gases and propellants for different propellant systems (monopropellant and bipropellant systems).

In: Proceedings of the 5th International Conference on Space Optics (ICSO 2004), Toulouse, France. Ed.: B. Warmbein. ESA SP-554, Noordwijk, Netherlands: ESA Publications Division, ISBN 92-9092-865-4

A new concept of a high-resolution near-IR spectrometer consisting of an echelle grating combined with an acousto-optic tunable filter (AOTF) for separation of diffraction orders, is developed for space-borne studies of planetary atmospheres. A compact design with no moving parts within the mass budget of 3-5 kg allows to reach the resolving power 20 000-30 000. Only a small piece of spectrum in high diffraction orders can be measured at a time, but thanks to flexibility of the AOTF electrical tuning, such pieces of spectrum can be measured randomly and rapidly within the spectral range. This development can be used for accurate measurements of important atmospheric gases, such as CO₂ in terrestrial atmosphere, isotopic ratios and minor gases. A spectrometer, based on this principle, SOIR (Solar Occultation InfraRed) is being built for Venus Express (2005) ESA mission. Instruments based on this principle have high potential for the studies of the Earth, in particular for measurements of isotopes of water in the lower atmosphere, either in solar occultation profiling (tangent altitude <10 km), or observing solar glint for integral quantities of the components. Small size of hardware makes them ideal for micro-satellites, which are now agile enough to provide necessary pointing for solar occultation or glint observations. Also, the atmosphere of Mars has never been observed at local scales with such a high spectral resolution. A laboratory prototype consisting of 275-mm echelle spectrometer with Hamamatsu InGaAs 512-pixel linear array and the AOTF has demonstrated a resolving power of 30 000 in the spectral range of 1-1.7 µm. The next set up, covering the spectral ranges of 1-1.7 µm and 2.3-4.3 µm, and the Venus Express SOIR are briefly discussed.

A paper originally presented by EADS Astrium at the 55th IAC in Vancouver in October 2004.

On October 26^th of next year, Venus Express spacecraft will depart from Baikonur on-board the Soyuz/Fregat Launch Vehicle. It will be the very first European mission to the "morning star", two years after the first European trip to Mars. Venus Express will carry 7 science payloads dedicated to global investigation of the Venusian atmosphere.

A paper originally presented by EADS Astrium at the 54th IAC in Bremen in September 2003.

On 28 January 2003, EADS Astrium officially signed the Venus Express contract with the European Space Agency (ESA) worth 82.4 million Euros for the design and development of the spacecraft. This will be the first European spacecraft to visit the planet Venus. Venus Express is scheduled for launch from the Baikonour Cosmodrome in Kazakhstan in November 2005. It will be launched by a Soyuz-Fregat rocket and put immediately into its transfer orbit to Venus.

Ultraviolet spectroscopy from the Pioneer Venus Orbiter shows a decline in the cloud top abundance of SO₂ from about 100 ppb to about 10 ppb in the period 1978-1986. A consistent decline in polar haze has occurred over the same period, with the correlation coefficient between these two observables of r = 0.8. Star calibrations determine the instrument sensitivity to within 10%, which rules out the possibility that this is an instrumental effect. Systematic errors could increase the SO₂ abundance to twice the inferred values in later orbits. Tracking of SO₂ features and power spectral analysis give rotation periods for the longer-lived features of 3.6-5.2 days, consistent with cloud-tracked winds observed at other wavelengths. The behavior of SO₂ and polar haze can be plausibly explained by episodic injection of SO₂ into the cloud top regions, for example, by active volcanism.