To catch a comet – the Rosetta Mission
The European Space Agency (ESA) launched the Rosetta spacecraft from Earth in March 2004. It then took Rosetta 10 years to catch Comet 67P.
Landing Philae
Rosetta Mission scientists used early images of Comet 67P to create a virtual model of the comet. This virtual model was used to pinpoint the best place to land Philae, the lander. Avionics engineer Warwick Holmes describes the process of landing Philae and the unexpected touchdown results.
On 12 November 2014, history was made when the Philae probe, carried by Rosetta, was successfully dropped onto Comet 67P. This was the result of decades of research, production and testing involving thousands of people from around the world.
Every single one of you is made of cometary dust from the elements of a supernova explosion more than 4.5 billion years ago. How did we all get here? How can we make a spacecraft to go back and land on a comet?
Avionics systems engineer, Warwick Holmes
Rosetta and Philae
Pre-launch testing
The Rosetta spacecraft needed to be able to survive the rigours of launch and extreme temperatures from -200°C to 300°C. Avionics engineer Warwick Holmes talks about his role in building and testing the spacecraft for the Rosetta Mission.
The Rosetta spacecraft is also referred to as an orbiter. Now Philae has landed on Comet 67P, Rosetta continues to orbit the comet, transmitting data from Philae and from its own scientific instruments back to Earth. Three purpose-built satellite dishes on Earth receive the data.
Rosetta is comprised of:
11 different scientific instruments
64 square metres of solar panels that can be rotated 180° to catch the maximum amount of sunlight (the Sun is a long, long, long way away!)
a port where the Philae lander was attached
a satellite dish and antennae
24 thrusters for trajectory and altitude control
a propulsion system with two large propellant tanks for fuel and the oxidiser.
Post-launch testing
The Rosetta spacecraft was subjected to vigorous testing prior to launch. The testing then continued after the Rosetta was launched in 2004. Scientists used every opportunity on Rosetta’s 10-year journey to Comet 67P to test various components of the spacecraft.
Rosetta mission engineer Warwick Holmes explains some of the tests.
Point of interest
Warwick refers to the distance from Sydney to Melbourne. In a New Zealand context, this would be the distance from Whangarei to Wellington or from Nelson to Dunedin.
Philae – the smaller landing module – is about the size of a home washing machine. It carries scientific instruments for nine different experiments and a drilling system to collect samples from the comet.
Rosetta and Philae were built to withstand huge variations in the environments they’d encounter over the 12 years of the mission. They required years of testing prior to launch, and testing continued on the long journey to Comet 67P.
Want a career in the space industry?
The Rosetta Mission has employed thousands of scientists, engineers and technicians from around the world. Do you fancy the idea of being part of a team to launch a spacecraft into orbit? Listen to avionics systems engineer Warwick Holmes and others on how they launched their careers in space.
Peter Beck: Becoming a rocket engineer
Kelvin Barnsdale: Turning a hobby into a career
Dr Allan McInnes: Working as a spacecraft systems engineer
Want to work on a spacecraft?
Like many space scientists and engineers, Warwick Holmes was inspired to pursue a career in the space industry from a space mission – the NASA Moon landing in 1969. He says it’s important to be ordinary but committed.
Getting to Comet 67P
How to catch a comet
Comets move extremely quickly, and they’re an immensely long way away on the edge of our Solar System. At present, rockets do not have the capacity to travel at the speeds required or carry the fuel needed to catch a comet. Avionics engineer Warwick Holmes explains how the Rosetta Mission was able to achieve what appeared impossible by using a process called gravity assist.
After launching from French Guiana in 2004, it took Rosetta over 10 years to reach Comet 67P, which is on the outer edge of our Solar System
Scientists used a technique called gravity assist so Rosetta could hitch a ride with other planets. Gravity assist occurs when the spacecraft enters the orbit of other planets and uses their gravity to propel or kick itself forward.
Rosetta also had a lengthy 2 and half years of hibernation to limit its use of power while waiting for certain alignments. During hibernation, the spacecraft spun once per minute while it faced the Sun so that its solar panels could receive as much sunlight as possible, and almost all of the electrical systems were switched off.
To enter hibernation, scientists set four timers on board to 80 million seconds. Each was counting backwards to 0, with two required to reach 0 in order to wake the spacecraft up. As there was only enough electrical power to keep the timers running, they had to switch off the receivers. This meant that, even in an emergency, they could not wake Rosetta up. This is the first time a hibernation like this has been done in a deep space project, and the scientists were understandably very nervous about whether Rosetta would wake up.
Landing on the comet
First images of Comet 67P
When Rosetta finally caught up with and went into orbit around Comet 67P, an intensive imaging campaign began. Rosetta Mission engineer Warwick Holmes explains some of the powerful imaging technology that is on board Rosetta.
Point of interest
While images of Comet 67P were able to give scientists a glimpse of the surface features, they were also important for planning the landing spot for the Philae lander on board Rosetta (see video Landing Philae)
In January 2014, Rosetta came out of hibernation, and everyone was very excited. By August, it had caught up to Comet 67P and was able to undertake the first orbit of the comet. Rosetta then began the intensive science phase of the mission – collecting data on the comet.
The initial data collected from the comet helped the scientists and engineers work out the best place to land the Philae probe. It had to be landed so that its solar panels would receive enough sunlight to power the different experiments.
Comet secrets revealed
Upon touching down on Comet 97P, Philae began immediately to collect data to send back to Earth via Rosetta orbiting above the comet. The Rosetta lander also continued to collect data from her suite of instruments. Rosetta Mission engineer Warwick Holmes explains some of the early findings from the Rosetta Mission data.
Point of interest
One of the instruments on board both the Rosetta and Philae spacecraft is a gas chromatograph. To understand how this instrument works, watch Dr Katja Riedel on measuring gas concentrations
On 12 November 2014, Philae separated from Rosetta and began to descend from 22 kilometres above Comet 67P to its surface. For 3 days, Philae was able to send the first images and data back to Earth via Rosetta, before going into hibernation again.
On-going mission
On 13 June 2015, Philae woke up again, this time from its new home on the comet. Communications between Philae and the orbiting Rosetta have been intermittent partly due to issues with the position of aerials. Scientists are now working out how to get a more stable connection between the spacecraft. They also need to make sure the craft are safe, as the comet is getting closer to the Sun and becoming more active. Rosetta’s planned lifetime is about 12 years. After the comet reaches its closest point to the Sun in August 2015 and starts heading back towards the outer Solar System, the plan is for Rosetta to land on the comet in December 2015 to complete some final experiments. It is expected to run out of fuel and die some time in 2016.
Update – the end of Rosetta
A carefully controlled crash landing into the comet occurred on 30 September 2016, bringing an end to the Rosetta mission. Additional science data was collected in this final phase as Rosetta descended into the comet. See the European Space Agency website for further information.
Scientists now have years of work ahead of them analysing the mountains of data collected during this mission.
Find out more about Comets.
Nature of science
The Rosetta Mission has been possible because of the development of new technologies. This shows how technological developments can change the types of evidence that can be collected, which can lead to new understandings about the world. Evidence from the Rosetta Mission will contribute to our understandings about comet composition and, ultimately, the beginnings of the universe.
Useful links
Stay up to date with the Rosetta Mission, with these blogs from the European Space Agency website.
Find out more using this interactive 3D visualisation of Rosetta’s journey and get in close with an interactive 3D visualisation of the comet on the European Space Agency website.
