Bill Dunford, over at the Planetary Society, has posted a super-nice composite of VMC images. Great work, Bill!
Effective immediately, all VMC images - past, present and future - are released by ESA under a CC license.
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Credit: ESA - European Space Agency, CC BY-SA 3.0 IGO
It's been a busy week for Mars with the announcement that NASA's Curiosity rover has made the first definitive detection of Martian organic chemicals in material on the surface (see "NASA Rover Finds Active and Ancient Organic Chemistry on Mars"). We've known for some time that there's methane in the atmosphere (see "Mars Express confirms methane in the Martian atmosphere"), but this is the first confirmation of organic carbon in a rock on Mars.
Our own (much more modest!) contribution to Mars news this week comes right here at the VMC blog. We are delighted to announce that, in addition to the full image sets in Flickr, the entire VMC RAW-format image archive is now available for download.
The archive contains the unprocessed versions of every image the VMC camera on Mars Express has ever taken since launch back in 2003. These include the 2003 Beagle separation images, the Earth observation from 2014 and the images used to create the 2012 full orbit videos!
The data are available in two ways:
- There are zip files containing the full image set for each individual observation with the date and time of the observation in the zip file name; these are arranged in folders for each year/month with subfolders containing that month's observations.
- We also have full yearly sets of observations for download to make it easier for those who want to get the entire dataset; note the gap between 2003-2007 is due to VMC not being used in this period.
These files are contain exactly what was/is sent back to Earth from Mars Express. The only processing performed by the mission team at ESOC is to extract the image data from the packets received from the spacecraft and assemble these into the individual raw-format image files (as each image is split across several packets). As a result, anyone who wants to have a go at processing these files is working with genuine raw spacecraft data.
Note that for Flickr, we currently run the downloaded images through a standard set of tools to adjust contrast sharpness and colour levels – exactly the same processing is done for every image VMC acquires. While this produces some good pictures, it is clear that tailoring processing to a specific image can bring out even more details and an even better end result.
We invite you to give it a try! Some of the best VMC images we have seen have been those processed by members of the public.
Further information about the image format and about VMC itself can be found in our FAQ page.
— VMC - Mars Webcam (@esamarswebcam) September 25, 2014
More cool news
The other big upgrade we can announce is that the extraction and upload of the files downloaded from Mars Express – both to the raw archive and Flickr – has now been automated such that the images will be available in both archives within hours of them arriving on Earth, day or night.
This automated process is also now connected to the @esamarswebcam Twitter account, so when new images are uploaded, anyone who follows this account will be notified straight away! So, really, following the @esamarswebcam Twitter account is the best way to be kept up to date with VMC images as they are delivered live from Mars!
– Simon Wood
MEX Spacecraft Operations Engineer
On behalf of ESA's entire Mars Express team, Welcome Maven! We thought you might enjoy a whole-disk image of your new planetary home.
NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft successfully entered Mars’ orbit at 04:24 CEST on 22 September 2014. This image was acquired by the low-resolution VMC camera on board Mars Express at 14:50 CEST on 20 September, when MAVEN was an estimated 312,000 km from Mars.
As you have seen from our recent blog posts and Flickr updates, VMC has been busy capturing some spectacular views of Mars.
However on 3 July, we once again turned away from Mars to look towards a more distant target.
Ever since our successful test of the VMC camera's long exposure mode (which brought us our first direct images of Phobos), there's one observation we've been keen to attempt:
An image of Earth!
Our chance observation of Jupiter in April served double duty as a dry run to evaluate if VMC stood a chance of detecting the famous pale blue dot.
With the success of the Jupiter pictures, we felt there was a good possibility that, whilst Earth would likely be faint, it would just be visible.
However, imaging Earth from a Mars-orbiting spacecraft using a camera with no specialised optics is not as simple as it sounds. So we thought we'd provide a brief overview of the kind of things that go into taking a picture like this.
One of the first issues we had deal with was determining the optimal time to take the photo.
Earth and Mars are both orbiting the Sun at different rates, so the angle between them regularly gets larger then smaller.
The larger the Mars-Sun-Earth angle, then – when viewed from Mars – the larger the percentage of Earth that is illuminated. So, you might conclude that we should take the image when this angle as big as possible.
However there are two problems with this:
- If this angle is very large, then Earth is much further away from Mars and thus will appear much smaller.
- The larger this angle gets, when we look towards Earth from Mars, the narrower the Mars/Sun angle gets. This means that the Sun will then be in the field of view of the camera.
This is not only prohibited in the interests the safety of our instruments but would also mean imaging something as faint as the Earth would be impossible as the light from the Sun would blind the camera.
The problem is illustrated below.
So what we needed was some middle ground, a period where the angle is large enough such that a sufficient amount of Earth is illuminated, but not so large that the Sun is too close to the camera's field of view.
With the help of JPL's HORIZONS solar system ephemerides computation service we were able to work out that the solid angle of the illuminated fraction of Earth was at its maximum on 21 June this year. We then tried to find an observation opportunity as close to this date as possible.
To keep the Sun as far from the camera's field of view as possible, it was decided we would not aim to have the Earth in the centre of the image, but instead offset it by 10 degrees.
The next issue we encountered was the need to tell the spacecraft to point VMC at Earth.
On Mars Express, our instrument platform is fixed to the spacecraft, so to point our instruments at a particular spot we have to turn and point the entire spacecraft.
To determine where we point the spacecraft, first the instrument teams have to tell our Science Planning team based at ESAC, in Spain, where they want their instruments to point and when. This is processed by the science planners and then sent here to ESOC to the Mars Express mission planning team.
Our mission planning system takes in all of the pointing requests that our science planners have sent, analyses them to check for critical factors like power consumption, illumination of the solar arrays and data generation as well as other constraints and requirements.
If all checks are OK, one of the outputs is a list containing an entire month's set of spacecraft pointings.
To fit in with this process, we generated a single new VMC 'Earth' pointing by using a software tool we developed ourselves. This new pointing was then added to the monthly list sent by the science planners and processed and checked by the mission planning system.
This set of spacecraft pointings is then sent off to the flight dynamics team here at ESOC. They are able to determine the spacecraft's exact position at any point in time.
Combining this information and knowledge of the spacecraft layout and the position of each instrument, they are able to calculate the orientation the spacecraft must have for it to point a specific instrument toward its desired target.
These calculations are performed for an entire month of observations, while checking that the pointings do not violate any safety constraints. Implementing, maintaining, enforcing and providing strict constraints protects delicate optics and sensors against the perils of excessive heating and over-illumination by the Sun.
As with all spacecraft pointings, our custom Earth pointing had to pass these strict tests for us to be permitted to attempt the observation.
After flight dynamics completed their analysis, the results were then returned back to mission planning, where they can be converted into sets of commands for the spacecraft's attitude and orbit control system.
Once these commands are generated they are checked by the mission planners and the flight control team before being uplinked to Mars Express (once per week).
At this point, the observation has been scheduled, the pointing commands have been generated and checked and up-linked to the spacecraft and the final stage was to then create the command sequence to operate the camera.
This involves telling it when to switch on, how many images to take, the exposure settings to use and when to switch off – and to tell the on-board computer to generate a report of the amount of data the observation produced to enable us to keep track of the volume of stored data on board the spacecraft.
As we expected Earth to be faint, and to maximise our chances of getting a decent image, we decided to use the same settings as our Jupiter pictures, as they contained a wide range exposures from 30 seconds down to 2 seconds.
Once this is all on board the spacecraft, we then have to wait until the images are taken and then down-linked, where we can then run them through our processing tools.
So after all that, here it is.. the Earth, at a distance of 150 031 705 km taken on 3 July 2014 at 15:52 CET from orbit around Mars.
The bright patches you can see are sunlight hitting the top of the recess VMC sits in and then being reflected off the camera lens.
However, on the 2-second exposure, this glare is reduced sufficiently to leave Earth clearly visible in the middle left of the image (Note: the colours here are the result of the processing tool we run the VMC images through).
At first glance it doesn't look like a particularly exciting photo. Some lens flare and a small faint dot are visible.
However, remember: there are 7 billion people living on that small faint dot!
This quote from Carl Sagan describing the famous Voyager 1 photo 'pale blue dot' sums it up rather nicely:
Consider again that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every 'superstar,' every 'supreme leader,' every saint and sinner in the history of our species lived there.
As usual, these images along with every other photo VMC has taken are available on our flickr channel.
Editor's note: Thanks to Simon Wood and the entire MEX team for these excellent images and report.
Excellent views of Mars acquired by the VMC today at 07:00 CEST (05:00 UTC), and downloaded within hours, transmitted to ESOC in Darmstadt, processed by the Mars Express team and... here it is! Thanks to the MEX team and Simon Wood.
Hot on the heels of yesterday's images, here are today's set fresh off the spacecraft; again we see possible clouds/dust round the poles.
These images were taken at an altitude of 9900 km above the surface at 07:00 CEST (5:00 UTC) this morning and transmitted back to Earth at 13:15 CEST (11:15 UTC).
This rapid turn around is in part due to the current Earth - Mars distance being 'only' 123 336 112 km. At this distance it only takes 6 mins 51 seconds for signals travel from the spacecraft to Earth. (As we get further away this can increase to up to 25 minutes.)
This proximity gives us higher data transmission rates, which mean we can transmit more of the stored data from the science instruments – and thus occasionally leaves us with spare data downlink capacity in some of our ground station passes. This spare capacity enables us to schedule the VMC data dumps much closer to the VMC observations.
Continuing from yesterday's highlighting of the Phoenix lander, here we have marked the landing site of the NASA Mars Exploration Rover B - Opportunity.
Opportunity is a fellow seasoned Martian explorer; it was launched only 5 days after Mars Express on 7 June 2003, landing on 25 January 2004 – one month after we entered Martian orbit.
Its landing site is located in the Meridiani Planum, an area of interest due to concentrations of the mineral Hematite, which on Earth is often formed in the presence of water.
With the possibility of water-formed minerals located here, it is not surprising that this is an area also investigated by our mineralogical Spectrometer OMEGA and our high resolution camera HRSC.
As with Phoenix, its sister rover Spirit and, currently, Curiosity, Mars Express has performed communication activities with Opportunity over the years, including the relay of the image above from the surface back to Earth.
It’s been quiet on the VMC front over the last few months, but the good news is that our next VMC observation is scheduled for mid-May. However, don't think we haven't been busy behind the scenes in the meantime!
In the summer of 2013, with the prospect of comets ISON and Siding Spring passing by Mars over the next 12 months, we wanted to have the ability to image them with VMC (if we got the opportunity). VMC has two operating modes: line mode and frame mode; the main difference between these is the image exposure times that can be set.
Line mode gives a maximum exposure of 200 millisseconds, and frame mode ranges from 200 milliseconds up to 95 seconds. The original on-board control procedure (i.e software commands) that operates VMC was only able to use line mode. This was a deliberate decision when the procedure was created to keep it as simple as possible, and 200ms is more than adequate for taking pictures of a well-illuminated Martian surface.
However, attempting to capture something as faint as a comet with a 200ms exposure on a 640x480 camera with no fancy optics was clearly going to be impossible. Thus the team decided this would be a good opportunity to perform a software upgrade that would enable us to operate VMC in both modes. Following a redesign of the algorithm, recoding and a period of validation against the spacecraft simulator, the upgraded procedure was uploaded to Mars Express. Once on board, the final step was to use it operationally.
A set of test images would be have to be taken and for this we needed a suitable target. The target had to be something bright enough that we stood a chance of imaging it but faint enough that we would likely be unable to see it on a short exposure. This was tricky given the limited number of test opportunities we had, but to our surprise and delight we discovered that Mars moon Phobos would pass through our field of view during the last of the slots we had identified .
Given that the last time long exposures were used on VMC was in 2007 (then just as a test to check it still worked) we had little information to go on regarding what exposure settings to use. The choice was further complicated by only having enough time to take 3 images.
In the end we decided on a large spread with 13-second, 6-second and 2-second exposures, as these would give us a good chance of capturing Phobos whilst also allowing us to assess the performance of the camera.
It was a tense wait to get the images back and see if all our work had paid off. Turned out we needn't have worried: not only had the upgraded software worked perfectly, but VMC had taken its first direct images of Phobos! We were absolutely thrilled with the results.
We estimate that we were approximately 8000 km away from Phobos when the images were taken (the increase in size/brightness is due to the different exposure times used). The 13-second and the 6-second images are a little over exposed (the glow in the bottom of the images is the light from the day side of Mars). In the final image (a 2-second exposure) it is possible to get some indication of the overall shape of the Martian moon. Putting all images together in an animation, Phobos can be seen moving across the field of view.
Unfortunately, our follow up observation of ISON did not go as well as we'd hoped. In the end, it was not as bright as originally expected and simply too faint to detect even with longer exposure times. All was not lost though, as we were left with these great shots of Phobos and new and proven imaging opportunities for VMC!
– MEX Team
Just in time to celebrate the 10th anniversary of Mars Express: a new and enhanced Full Orbit Video delivered by the VMC camera - the Mars Webcam!
The version below is a special 'MEX birthday preview' – we'll post a somewhat extended version late next week (along with a more detailed explanation on how this video was produced), to coincide with the next expected VMC image set arriving from Mars.
What's the 'Full Orbit video', you ask? Access the original FO video produced in 2010 for the full description.
Thanks to the Mars Express Science & Operations teams for generating a fabulous, unique-in-our-Solar-System view of the Red Planet.
Happy Birthday, Mars Express!