Bill Dunford, over at the Planetary Society, has posted a super-nice composite of VMC images. Great work, Bill!
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.
Today's post contributed by Mars Express operations engineer Simon Wood – Ed.
Here in our latest Mars Webcam images taken yesterday, 4 June, we have not only captured more shots of the northern polar cap and what seems to be further dust/cloud formations around the pole, we have also snapped some of the biggest geological features on the planet.
In this image, we have all three volcanoes that make up the Tharsis mountains.
These three volcanoes dwarf anything found on Earth, ranging from 14 to 18 km in height. To put this into perspective, the tallest volcano on Earth is Mauna Loa in Hawaii, which only reaches 9 km above the ocean floor.
However, the Tharsis mountains are themselves dwarfed by the largest volcano on the Red Planet (and indeed in the solar system), Olympus Mons, which has an approximate height of a staggering 25 km!
The favourable lighting conditions in yesterday's observation enabled the entire base of the volcano to be visible and if you look closely you can even make out the crater. Olympus Mons covers an area of around 300 000 square kms, which to give some indication of the scale, would cover most of France.
We also just see the edge of the 'Grand Canyon of Mars' the Valles Marineris running along the limb of the planet (hopefully we'll have more on that in a forthcoming observation).
And here's a very cool Valles Marineris fly-through video:
One further item we've tagged in our image is the landing site of NASA's Phoenix spacecraft, the first spacecraft to send back science data from the Martian poles.
In May 2008, Mars Express provided communication relay support to Phoenix using MELACOM, our UHF radio, recording its radio signal during the entry, descent and landing phase (just as we would later do for Curiosity in 2012).
Some further relay tests were performed once it was successfully on the surface, with our last contact completed on 31 May 2008.
As usual all the images are available on the VMC flickr account: http://www.flickr.com/photos/esa_marswebcam/
A couple weeks, ago we ran an additional test of our long exposure settings on VMC. This time, we we upped the image exposure to 30 seconds.
Just like with our Phobos images, its best to have a target to look at and for this test we used Jupiter.
We found that, not only was Jupiter visible on just a 2-second exposure, but on the longer ones Jupiter was also visible together with the two twins of Gemini, Pollux and Castor.
So in this set we have our first image of a planet other than Mars and also our first confirmed imaging of stars!
The full image set along with all our other VMC images are in our Flickr channel.
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!
Quick update received on 11 March from Mars Express operations engineer Andy Johnstone - Ed.
On 7 March, we were scheduled to perform a MELACOM pass with NASA's MSL; this involves us passing over Gale Crater with our MELACOM UHF antenna pointed towards the rover.
NASA later chose not to use our pass, so we decided to use it to perform a VMC observation instead.
The images we took were then stitched together to form a short video where Gale Crater can be seen as the dark horseshoe shape midway up the left hand side of the screen. This offset is due to VMC being set at 19 degrees from MELACOM.
With not too much fanfare, December saw the Mars Express mission operations team at ESOC bringing the VMC back online, again. You'll recall that VMC went offline in late 2011 when Mars Express suffered problems with the mass memory storage. The spacecraft and instruments were fully back in routine operation by January 2012, meaning that the team could then devote some 'time-available' time to recommissioning VMC. In addition to getting the camera itself running (marked by the first symbolic data transmission of a VMC image via Malargüe station), we also set up a new blog channel and a dedicated Flickr page to host the images (and the Twitter account – @esamarswebcam – is still running).
Over at the Planetary Society blog, Emily Lakdawalla posted an update explaining the return of the VMC and including comments from Daniel Lakey, one of our MEX engineers looking after VMC. There's little improving on her excellent report, so with no further ado, please (a) take a look at her gorgeous collage '56 views of Mars from the Mars Webcam in 2012' reproduced below, and (b) head over to her blog and read her update in full.
Following the first downlink over Malargüe tonight, we will consider the Flickr page to be open for business. Unfortunately, due to the upcoming solar conjunction and associated low bit-rate season, we're unlikely to get any downlink slots for VMC for a few months, but once the Mars Webcam is taking pictures again, the images will be published for the world to see within seconds of them being received on Earth. The low priority of VMC images means that their downlink to Earth can be some time after the observation.
-- Daniel Lakey, Mars Express, 18 Dec 2012
Marking its inauguration, ESA’s Malargüe tracking station receives Mars Webcam image.
An image of the enigmatic Red Planet acquired by ESA’s Mars Express on 15 December 2012 was downloaded via ESA’s new tracking station in Malargüe, Argentina, symbolising ‘first data’ and recognising formal inauguration.