First Contact! Mars Express’ first ‘conversation’ with Curiosity

As we reported yesterday, Mars Express had a busy Sunday evening, pointing first at NASA's Curiosity rover on the surface of Mars and then swinging around to do another relay pass with Opportunity. We received the data from both of these passes this morning over ESA's New Norcia ground station and, on first look, it seems that both relays were very successful.

First Laser-Zapped Rock on Mars

First Laser-Zapped Rock on Mars. This composite image, with magnified insets, depicts the first laser test by the Chemistry and Camera, or ChemCam, instrument aboard NASA's Curiosity Mars rover. The composite incorporates a Navigation Camera image taken prior to the test, with insets taken by the camera in ChemCam. The circular insert highlights the rock before the laser test. The square inset is further magnified and processed to show the difference between images taken before and after the laser interrogation of the rock. The test took place on Aug. 19, 2012. Credit: NASA/JPL-Caltech/LANL/CNES/IRAP

In ESA's MEX team, we're particularly excited to have had our first contact with Curiosity – proof that the amazing new rover from the United States can talk with our veteran European Mars orbiter!

At the start of the contact, Mars Express was over 3600 km from Curiosity's landing site in Gale Crater and closed in to only 1300 km by the end of the contact – streaking across the sky as seen from Curiosity.

During this overflight by Mars Express, it 'hailed' Curiosity in Gale Crater and the rover responded. The two spacecraft then autonomously established a link with each other and Curiosity flowed data back to Mars Express for nearly 15 minutes. This international chat between two spacecraft in deep space is proof of all our preparation, standardisation and cooperation work in action – so it's something both agencies can be proud of.

ESA's first 35-metre deep-space ground station is situated at New Norcia, 140 kilometres north of Perth in Australia. The 630 tonne antenna will be used to track Rosetta and Mars Express, the latter to be launched in 2003, as well as other missions in deep space. The ground station was officially opened on 5 March 2003 by the Premier of Western Australia, Hon Dr Geoff Gallop. Credits: ESA

ESA's first 35-metre deep-space ground station is situated at New Norcia, 140 kilometres north of Perth in Australia. The 630 tonne antenna will be used to track Rosetta and Mars Express, the latter to be launched in 2003, as well as other missions in deep space. The ground station was officially opened on 5 March 2003 by the Premier of Western Australia, Hon Dr Geoff Gallop.
Credits: ESA

The actual data that flowed back was made available to NASA earlier today, who will now retrieve and process the data.

Hopefully we'll have some info from them in the next couple of days about what exactly was contained within. We'll also receive (within Tuesday) the 'housekeeping' telemetry of Melacom – information on how our radio performed. This will allow us to double-check the performance of this first important contact with Curiosity.

The data was sent at a rate of only 8 kbps – 125 times slower than the 1-Mbit/second Internet connection you might have at home!

We wanted to take things easy to start with, though, and test the performance of the link. Nonetheless, we received 955 data packets from Curiosity, totalling 867 kilobytes of data.

This will be the first of several contacts with Curiosity in the future, as we better learn how to use and optimise this relay link between the two craft and the two space agencies. Watch this space for more details as we get them on this pass and the future contacts between Mars Express and Curiosity.

 

Melacom – Europe’s voice & ears at Mars

Melacom

A photo of the Melacom UHF communications package carried on Mars Express. Credit: QinetiQ

When Curiosity lands on Mars, the radio receiver on Mars Express which will be listening in is Melacom. This radio was developed for Mars Express by the UK company, QinetiQ in order to support the Beagle-2 lander which was carried on Mars Express.

Sadly the Beagle-2 lander failed to land successfully, but the Melacom lander communications package was not wasted and has been used to contact every single Mars lander to successfully land since the Mars Express launch in 2003.

Mars Express has a large X-Band and S-Band radio system that lets it talk to Earth, but Melacom was specially designed as a separate UHF radio system to let it talk to landers on the surface of Mars. The radio supports a number of different modes, including the ability to hold a two-way data communication with a lander and the open loop mode we described earlier. It implements a standard known as Proximity-1, developed by CCSDS - an international committee that works on standards such as this to ensure that any spacecraft can talk to any other, such as the European Mars Express and the American Curiosity [more details on the excellent work done at CCSDS by ESA, NASA and other agencies here - Ed.].

Melacom Communications System Installed On- board Mars Express

Another shot of Melacom after installation on Mars Express, taken while the spacecraft was being built.

The radio has been used successfully many times, including open loop recording of JPL's Phoenix lander as it landed on Mars in 2008.

In preparation for the arrival of Curiosity, our in-flight testing intensified and we've conducted a number of demonstration passes with NASA's Opportunity Mars Exploration Rover, operated by JPL. During these passes we demonstrated the ability of spacecraft from two agencies to coordinate and work together at Mars, exchanging telemetry data and commands and conducting recordings.

In anticipation of the arrival, a team from QinetiQ also took a test model of the Melacom radio to JPL to perform ground compatibility testing with a similar model of the Curiosity radio. Through all of these activities, we're confident that we'll all be speaking the same language at Mars when Curiosity arrives tomorrow.

To learn a lot more in depth information about the Melacom radio and our support of the Curiosity mission using it, take a look at this conference paper by our Melacom engineer, Olivier Reboud.

What is Open Loop Recording?

How Mars Express will listen to Curiosity

3-D waterfall diagram showing the open loop recording made by Mars Express of MER-B (Opportunity) during the rehearsal overflight for Curiosity EDL.

You'll see a lot on our coverage of the Curiosity landing about Open Loop Recording,' something which was hinted at in a previous post about the difference between 'signal' and 'data'.

OLR refers to the type of recording that will be made by Mars Express as Curiosity descends towards Mars, and in parallel by ESA's New Norcia station here on Earth.

In open loop recording, we don't try to decode the bits and bytes being sent by the descending lander but instead try and listen to as much of the radio spectrum as we can, hopefully detecting the tone of the lander's transmissions within this spectrum. Think of it like listening to a crowd of people – you can either focus on the words one person is saying, or listen to the whole crowd to get a full picture of what's going on; that's what we'll do with open loop recording.

On Mars Express we'll use our UHF Melacom radio to listen in on the UHF part of the spectrum – usually used on Earth for radio and television transmissions; it's also used at Mars as the frequency that different orbiters and landers use to talk to each other.

From New Norcia we'll be listening to the X-Band part of the spectrum – used on Earth mainly for radar systems but also as a way of communicating with spacecraft across the solar system (Mars Express uses X-Band for its main link back to Earth).

Each of these parts of the spectrum is actually a wide range of frequencies and in open loop we listen to as many as possible, creating a diagram like the one in the picture above.

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Difference between ‘signal’ and ‘data’

Mars Express orbiting the Red Planet - artist's impression Credit: ESA/Alex Lutkus

Mars Express orbiting the Red Planet - artist's impression Credit: ESA/Alex Lutkus

If you read the web article last week announcing the planned support by Mars Express for NASA's MSL landing on Mars  (see ESA's Mars Express supports dramatic landing on Mars), you may have come away with the impression that Mars Express will receive actual data transmitted by MSL during entry descent and landing.

As pointed out by Michael Khan, a mission analyst at ESOC, the way the article is worded is not actually wrong. However, anyone who doesn't know the technical details might get the wrong impression.

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