Venus Express Frequently Asked Questions (FAQs)

About Venus Express

Where does the name ‘Venus Express’ come from?
The name Venus Express comes from the short time to define, prepare and launch the mission. It will take less than three years from the approval to the launch of the mission. To do this, ESA re-used the same design as the Mars Express mission and the same industrial teams that worked on that mission.

What are the mission objectives? What scientific return do you expect from the mission?
From orbit, Venus Express will scan the cloud tops and peer through the atmosphere of the planet. In particular it try to answer the following questions:

• How do the complex global dynamics of the planet work?
  - What causes the super-fast atmospheric rotation and the hurricane-force winds?
  - What maintains the double atmospheric vortex at the poles?
• How does the cloud system work?
  - How do clouds and haze form and evolve at different altitudes?
  - What is at the origin of mysterious ultraviolet marks at the clouds tops?
• What processes govern the chemical state of the atmosphere?
• What role does the ‘green-house effect’ play in the global evolution of the Venusian climate?
• What governs the escape processes of the atmosphere?
• Are there water, carbon dioxide or sulphuric acid cycles on Venus?
• What caused the global volcanic resurfacing of Venus 500 million years ago?
• Why are some areas on the surface so reflective to radar?
• Is there present volcanic or seismic activity on the planet?
• Why Venus rotates backwards and so slowly, just one revolution every 243 Earth days?
• Why is the planet’s magnetic field so weak?

What can the study of Venus bring to our everyday life on Earth?
Comparative planetology can bring a lot to our understanding of Earth and our environment. Venus and Earth could have been expected to be similar (and may have been in their early histories), but we do not know why they evolved so differently.

If their atmospheres were very similar in the beginning, then obviously something changed on Earth or on Venus, but we do not know what or when. Moreover, the 'greenhouse effect' alone cannot account for today's extreme conditions on Venus.

Most importantly, the combined knowledge of structures, chemistry and dynamics of planetary atmospheres, such as Venus, Mars and Titan, will help in better understanding Earth's atmosphere and improving our climate models.

What makes Venus Express special?
Venus Express is special because it aims to study the Venusian atmosphere and clouds in unprecedented detail and accuracy. It is ESA's first spacecraft to visit this planet.

It is hoped it will also achieve several other 'firsts', such as:

• First global monitoring of composition of lower atmosphere in near-infrared transparency ‘windows’;
• First coherent study of atmospheric temperature and dynamics at different levels of atmosphere, from surface up to ~200 km;
• First measurements from orbit of global surface temperature distribution;
• First study of middle and upper atmosphere dynamics from oxygen (atomic and molecular), and nitrogen oxide emissions;
• First measurements of non-thermal atmospheric escape;
• First coherent observations of Venus in spectral range from ultraviolet to thermal infrared;
• First application of solar/stellar occultation* technique at Venus;
• First use of 3D ion mass analyser, high-energy resolution electron spectrometer and energetic neutral atom imager;
• First sounding of Venusian top-side ionospheric structure.

Were there lessons learnt on Mars Express that were applied to Venus Express?
The experience of Mars Express was and continues to be passed on to Venus Express. An example of a lesson in development was in the way that the 'startrackers' from Galileo Avionica were verified. On Mars Express, there were no 'stray light' tests, but this verification was improved on Venus Express by performing these very important tests.

Also the experience of ongoing operations on Mars Express are passed on to the Venus Express teams to determine their applicability to the Venus Express design and the future operations. In some cases, software modifications added to Mars Express after launch to improve the spacecraft functioning have already been applied to Venus Express.

How was the Mars Express design adapted to the environment of Venus?
Venus Express and Mars Express are very similar in design but some modifications had to be introduced on the spacecraft as the environment near Venus is harsher than the Martian environment. The solar flux is twice as powerful as it is in Earth orbit and four times as much as it is at Mars. As a consequence, thermal control has been changed dramatically.

Where Mars Express had about 10 thermal control zones, Venus Express has four times more to ensure the best working environment for the instruments. While Mars Express was wrapped into a black thermal insulation to retain some heat in the coldness of the outer Solar System, Venus Express bears 27 layers of kapton insulation with a shiny golden upper cover to evacuate as much thermal radiation as possible.

The solar arrays had to be redesigned too. They extend only half of the span of those on Mars Express despite the fact that their size was actually not dictated by the conditions upon arrival at Venus but at departure from Earth, where the solar flux is halved compared to Venus but nearly the double of its level at Mars.

To withstand the high thermal stress of continual pointing toward the Sun while around Venus, which could lead to thermal peaks at 250°C, the solar cells are arranged alternately with lines of tiny radiating mirrors to evacuate the excess heat. The backside of the arrays has also been protected against the reflection of the solar flux by the Venusian atmosphere.

The antenna system also had to be redesigned as the behaviour of Earth in the Venusian sky is very different from what it is as seen from Mars. For a probe orbiting the Red Planet, Earth is an inner planet and it appears always within 40° of the Sun.

This enables a rather simple pointing of both the solar arrays and the antenna in nearly the same direction. As seen from Venus, Earth is an outer planet, which can be in any direction relative to the Sun. To enable communications in any configuration, a second antenna (directly taken from the Rosetta project) was added on top of Venus Express, pointed in opposite direction to the high-gain antenna.

The payload has also been changed, as it includes only three instruments derived from those flown on Mars Express. The other four are either derived from instruments flown on Rosetta or new developments.

How much did Venus Express cost?
ESA’s investment is about 220 million Euros covering the development of the spacecraft, the launch and the operations. This amount also includes 15 million Euros as support to several research institutes for building the instruments. Together with Rosetta and Mars Express, Venus Express makes up a family of missions in which costs are shared.

By reusing the Mars Express design, you saved development costs, but how come the industrial contract for Venus Express was more expensive than for Mars Express?
You cannot compare missions to different planets that way. The extra costs result from the more hostile environment around Venus, which required additional thermal control and radiation hardening as well as the complete redesign of the solar arrays. By reusing existing hardware, ESA and the industrial team have been able to keep the cost of the mission at €220 million. If it had been developed from scratch, it would have cost more than €400 million.

Is there any plan to reuse the Mars Express design again for future missions beyond Venus Express?
Parts from the Mars Express platform are being reused for the ADM-Aeolus mission to study wind dynamics on Earth. There is no plan at the moment for another space science mission based on this design. However, such a reuse is not ruled out if there is a relevant mission concept which fulfils sound scientific objectives.

How long did it take the spacecraft to get to Venus?
The journey lasted 162 days. Venus Express was captured into an orbit around Venus by firing the main engine for 53 minutes. About five days later, a two-week long series of manoeuvres began putting the spacecraft into its operational orbit, circling above the poles of the planet once every 24 hours.

How long did Venus Express operate?
The primary mission consisted of two full planetary revolutions (Venusian ‘sidereal’ days) – equal to 486 Earth days – after Venus Orbit Injection. However, Venus Express was operational for more than 8 years!

What happened with Venus Express once the mission was completed?
At the end of its lifespan, the spacecraft first conducted some aerobraking tests in the upper atmosphere, before sinking deeper into the atmosphere and eventually burning up. Read the full story here.

How were the data collected by Venus Express distributed?
As for Mars Express, the Principal Investigators will get their data first, directly from their instruments and have a six-month exclusivity on them before they are freely released to the science community. The first data, however, will be presented by ESA together with the scientists. All the data from the mission are archived in a central repository at ESA.

I have a question that is not answered in this FAQ list. What should I do?
You can send your request here. Given the huge volume of questions we get every day, we cannot guarantee to answer every e-mail individually. If it's a question we've seen before, we'll consider adding it to our current FAQs list.