We're transfering the Mars Express blog to the new Wordpress platform. Effective immediately, all news, updates and information that would have appeared here in the 'old' MEX blog will be published via http://blogs.esa.int/mex.
Great news from the ESA ESTRACK team today!
The first-ever reception of signal took place at ESA's new 35m deep space station at Malargüe, Argentina, on 14 June. There's still a lot of work to be done to have the station fully comissioned, but this is an excellent achievement and an important milestone - and the signal came from our very own Mars Express, orbiting the Red planet some 193 million km away.
Roberto Maddè, the DSA-3 project manager, wrote:
We did a test 'shadow tracking' of Mars Express last week on 14 June, around 22.30 UTC.
The signal in L-band is shown in the picture (at left). We measured a signal/noise ratio of about 56 dBHz, which matches the levels obtained by ESA's existing 35m station at Cebreros during the same pass.
Pointing still needs to be optimised (pointing correction for our test was done manually); these tests are still 'qualitative'. Some quantitative tests (less news-worthy but more useful to understand whether the station is operating within specs) are being done and look promising. Now, the teams on site are recalibrating the beam waveguide mirrors; we'll have more tests in two weeks. But we need to calibrate the pointing first.
DSA-3 is set to enter regular service later this year.
You can see DSA-3 'live' via our webcam (also below) -- Daniel
On 30 April, in a carefully planned data-gathering exercise, ESA's Mars Express team used the passage of Phobos between Earth and the spacecraft to record precisely when a radio signal was blocked. The data may now lead to the best-ever determination of Phobos's orbit, knowledge that will help scientists better understand our planetary neighbour and its double-moon system.
You'll recall our earlier posting, when we described MEX team plans to take advantage of a rare alignment of Earth - Phobos - Mars Express to measure precisely when the bulk of Phobos would block radio communications between the spacecraft and ESA's 35m Cebreros station in Spain.
The prediction was that the 'occultation' would last around 12 seconds, from 21:21:22.9 to 21:21:34.1 UTC (spacecraft time). The predicted ground receive time was between 21:29:13.0 and 21:29:24.2 UTC (i.e. 7:50 mins later on Earth).
The activity took place as planned on Monday, 30 April.
Based on a reconstruction of the MEX orbit by ESA's Flight Dynamics team at ESOC, results indicate that the expected start time of the occultation by Phobos was 0.5 seconds earlier than that predicted. Similarly, the end time is 0.4 seconds earlier than predicted.
The plot below indicates the actual situation as measured very precisely from Cebreros station.
It shows the view from Earth of the 'expected' occultation of the MEX signal by Phobos. The large, grey-green circle corresponds to the moon's disk; it is shown (at this scale) as a circle having a radius of 13.4 km.
So why was the actual recorded occultation times a few seconds shorter than expected?
ESA's Trevor Morley, lead flight dynamics specialist for Mars Express, says there are two possible reasons:
- The best fit ellipsoid for the shape of Phobos has semi-axes of 13.4 x 11.2 x 9.2 km. The dashed circle shown in the plot has a radius of 9.2 km. The occultation duration depended upon the length of the chord across the real face of Phobos between the entry and exit points. The actual profile of Phobos needs to be applied to calculate this length (which is why photos/observations of Phobos are so important - Ed).
- A shorter than expected occultation duration would also occur if the present error in our prediction of Phobos's orbit is such that the moon's true position at the time was further towards the south.
Trevor says that the recorded timing data will now be shared with the MEX science team as well as with colleagues at NASA JPL; it is expected that they will be able to use these results to improve models of the Phobos orbit:
“The Phobos orbit model that we are presently using was generated by Bob Jacobson of JPL and is almost certainly the most accurate one available. We will provide Bob with all the signal data plus our determined orbit of MEX,” he added.
“Of course we can provide the data to any scientists working on this topic, including those who have been using directional data derived from Phobos images made by the MEX camera for the same purpose.”
Mars Express Spacecraft Operations Manager Michel Denis says:
It's part of the scientific method to make use of every opportunity to investigate our natural world.
Also, it's second nature and ‘pride of craft’ for the mission operators to figure out how to achieve more with the same resources– whether that’s a spacecraft or a ground station. In this case, we could also achieve ‘extra science’ through tight cooperation between several teams here at ESOC – flight dynamics, ground segment, flight controllers – and we were able to fine-tune, second-by-second, an already packed science and communication plan.
The team here have really done a nice job!
On Monday, 30 April, Mars Express mission controllers at ESOC will take advantage of a rare alignment of the spacecraft with Phobos and Earth to use radio signals to determine the Martian moon's orbit.
A (very) rough sketch of the alignment
If the team's careful planning and preparation pay off, the occultation of Mars Express by Phobos (as seen from Earth) will provide highly accurate data that can be used to determine Phobos's orbit with unprecedented accuracy, possibly improving it by a factor of 2.
Essentially, here's what's going to happen:
- On 30 April, Phobos will, for a few seconds, pass between MEX and Earth, blocking the direct line-of-sight path for radio signals transmitted from MEX to ESA's 35m deep-space station at Cebreros, Spain.
- In a pointing specially extended for this event, Mars Express will already be turned toward Earth —
a mere pale blue dot some 140 mn km away
and will already be transmitting a steady signal to Cebreros.
- Special radiometric recording equipment installed at the Cebreros ESTRACK station will record — with sub-second precision —
the start/finish time of the break in the transmission.
- The occultation is predicted to last just 12 seconds, from 21:21:22.9 to 21:21:34.1 UTC (spacecraft time). The predicted ground receive time is between 21:29:13.0 and 21:29:24.2 UTC (i.e. 7:50 mins later on Earth).
- Once the occultation ends, MEX will perform a 'high-speed' slew to re-orient itself so that the HRSC camera and other instruments are pointing toward Mars to conduct a regular observation pass over the Red Planet starting at 21:22 UTC.
"The occultation tracking promises to provide a very nice boost in our understanding of Phobos, an enigmatic body if ever there was one, without affecting routine science," says Mars Express Spacecraft Operations Manager Michel Denis.
We'll keep in touch with the Mars Express mission team at ESOC throughout the weekend and Monday/Tuesday to post any updates; you can also follow news via Twitter (@esaoperations).
The animation below shows what will happen immediately after the occultation tracking, when Mars Express re-orients itself for the Mars observation pass.
A quick link and extract from an update on Wednesday in ESA's Science directorate web pages; it provides a nice overview of the 'return to science' situation. References to our very own VMC camera activities highlighted - and note very nice comments on teamwork! Click link to read the full report.
Full report via ESA Science & Technology
While full science operations have now been resumed, a number of tasks remain to be completed. Most important among these is the implementation of an OBCP scheduler. This will enable the spacecraft to operate autonomously for up to a week, compared to the few days that are possible with the current FAST system. Work is also in hand to resume operation of the Visual Monitoring Camera (VMC – the 'Mars webcam').
Enormous team effort
Completely redesigning the way in which Mars Express is controlled has involved an enormous amount of work for the mission control team at the European Space Operations Centre (ESOC), assisted by their counterparts at the European Space Astronomy Centre (ESAC), PI-teams, other ESA experts and partners in industry. Everyone involved with the mission is extremely grateful for their hard work.
Although the 'Express' in Mars Express highlights that the mission was developed in a short time and with a relatively modest budget, the ability to resume full operations after a very serious failure shows that the resulting design is both robust and flexible.
Mars Express has now been restored to full operational capability and its potential mission lifetime remains unchanged
A nice New Year's post starting the year with a question (and answer!) on the fabulous high resolution stereo camera (HRSC) image of Orcus Patera, first published by ESA (here) in 2010, and reposted as the Image of the Day on 31 December 2011 at the Mars Travel blog. Best wishes to everyone for a healthy and successful 2012. Details below! -- Daniel
First, here's the image (click image to access the original post in ESA web):
Orcus Patera is an enigmatic elliptical depression near Mars’s equator, in the eastern hemisphere of the planet. Located between the volcanoes of Elysium Mons and Olympus Mons, its formation remains a mystery. Often overlooked, this well-defined depression extends approximately 380 km by 140 km in a NNE–SSW direction. It has a rim that rises up to 1800 m above the surrounding plains, while the floor of the depression lies 400–600 m below the surroundings.
Earlier today, Mars Travel blogger David Geaney sent in a question:
If you look at one of the central craters in Orcus Patera using the HRSC image, you will see there is something blue in the crater. What is the blue material? Thank you for your time and patience.
We passed the query to Mars Express project scientist Olivier Witasse, who wrote:
The blue is not a lake....
It's dust, which emits in the blue part of the spectrum. In the data processing, the blue part is somewhat enhanced, which sometimes creates a wrong impression.
A comment today from Mars Express Spacecraft Operations Manager Michel Denis on this week's report: "MARSIS completes measurement campaign over Martian North Pole." The report gives good news!
"The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument on board Mars Express has recently completed a subsurface sounding campaign over the planet's North Pole. The campaign was interrupted by the suspension of science observations several times between August and October due to safe modes and to anomalies in the operation of the spacecraft's Solid-State Mass Memory (SSMM) system. As MARSIS best observes in the dark, which for the North Pole only occurs every few years, it was among the first instruments to resume observations once a partial work-around for the problems had been implemented."
In his comment below, the 'FAST Method' that Michel refers to is the operations team's newly developed way of uploading commands to Mars Express, which avoids using the problematic Solid State Mass Memory (SSMM) for critical commanding.
The 'File-based Activities on Short Timeline' method essentially means that commands are grouped in very short self-contained files that can be loaded safely, in advance of execution, from the SSMM into an alternative memory unit (that is reliable but not as capacious as the SSMM).
The FAST method - loading short command files upon need into the short onboard mission timeline - was put into use at the end of October 2011 with the (excellent) result that we could save what was remaining of the North Pole observation campaign by the MARSIS radar.
The net loss in data collection was mitigated by using the existing MARSIS command sequences as soon as possible. Meanwhile, as for the other instruments, new MARSIS on-board control procedures (OBCPs) are under development and will allow operation with fewer commands, therefore enabling the operation of several science instruments in parallel.
My main point? We did our job: contrary to widespread received wisdom, the spacecraft operators' role is not to simply watch over (supposedly) boring routine operations during the many long years of a mission - nor simply saving a spacecraft that experiences problems. In fact, we are relied upon to deliver safely as much of the expected (precious) scientific data as possible within the resources available - despite adversity. And that's what we're doing!
This in this morning from Jonathan Schulster on the Mars Express operations team:
The ASPERA (Energetic Neutral Atoms Analyser) instrument high voltage (kV) lines and equipment were successfully switched on today, a few minutes ago at Mars (~09:57 CET), using the new on-board control procedures (OBCP).
These will run for one hour until 10:40CET today and the ASPERA science team will examine the recorded science data before giving the 'go-ahead' for full operations of ASPERA using only OBCP's starting 9 Jan uary 2012.
- Jonathan Schulster
Mars Express Mission Planning & Flight Control Team
Looks like another instrument is set to return to action! -- Daniel
Mission controllers are making excellent progress in returning Mars Express to routine service. Some science activities have already resumed after being temporarily suspended last month following a series of faults related to the onboard data storage system.
Having arrived around Mars in December 2003 for an initial two-year mission, the spacecraft is now in its eighth year of science operations. It has returned some of the most stunning images and valuable science data ever obtained from the Red Planet.
In mid-October 2011, anomalies in the operation of its Solid-State Mass Memory (SSMM) system caused science observations to be temporarily halted.
Anomalies in the operation of the solid-state mass memory system on board Mars Express have caused science observations to be temporarily halted. A technical work-around is being investigated that will enable the resumption of a number of observations and should evolve into a long-term solution.
In mid-August, Mars Express autonomously entered safe mode, an operational mode designed to safeguard both the spacecraft itself and its instrument payload in the event of faults or errors.
The cause of entering the safe mode was a complex combination of events relating to reading from and writing to memory modules in the Solid-State Mass Memory (SSMM) system. This is used to store data acquired by the instruments and housekeeping data from the spacecraft's subsystems, prior to its transmission to Earth, and is also used to store commands for the spacecraft that have been received from the ground stations, while awaiting execution.
At the moment when Mars Express, Phobos, and Jupiter aligned on 1 June 2011, there was a distance of 11 389 km between the spacecraft and Phobos, and a further 529 million km to Jupiter.
A nice wrap-up on Mars Express achievements today!
Mars Express Spacecraft Operations Manager Michel Denis sent in anote pointing out that, according to ScienceWatch.com, in the 'Top 10 papers on planetary science of the last 10 years', the most-cited papers (5 out of 10) are from Mars Express data and scientists (ranking 1, 2, 4, 6 and 9). In the same list, quite a number of papers are Cassini- and Huygens-related. Full details via: http://www.sciencewatch.com.
As Michel mentions, this is a nice continuation of the 'Top 10 Science Insights of the Decade' in the magazine Science (December 2010) where, with all sciences together, 'Wate on Mars' appears as one of the ten (with Mars Express mentioned by name!). -- Daniel
A few days ago, Dan Brennen, of Elk Grove, California, posted a very nice animation in the UnmannedSpaceflight.com forums and we are delighted to share this below. Dan sent us a description:
The animation was created using the sequence of 5 images located here which were scaled down to 1/5 size. A simple morphing program was utilized to create the intermediate images which allow for the appearance of motion. Approximately 30 control points were identified to tell the program where the limb had changed shape and key features on Phobos had moved between images. Each transition from one image to the next contained 200 steps, which was later compressed to 8 frames per second to create the final image file.
I'm sure you can guess that the quality would improved with more control points and more precise placement of those control points. But it's quite time consuming, especially with five images. So I did this with less time and effort in order to quickly create an interesting feature for our forum in just an hour or two while I had my Saturday morning coffee.
Thanks, Dan, for some great work! -- Daniel
Original animation via UnMannedSpaceFlight.com Original HRSC images: Copyright ESA/DLR/FU Berlin (G. Neukum). Animation credit: Dan Brennan, Elk Grove, California
But what I think is best about this particular set of images is that they serve as really great illustrations of how HRSC works. It's an unusual instrument: a pushbroom camera that acquires simultaneous stereo and color data with a higher-resolution framing camera bolted to it. If you don't understand what that preceding sentence means, bear with me; I'll explain.
Access Emily's full post in The Planetary Society Blog.
The team here were delighted to see that the Mars Express HRSC image of Phobos had been selected as NASA's Astronomy Picture of the Day (APOD) yesterday! Thanks guys!
Click on the image below to access the APOD site --> and scroll down and click on the link to vote for APOD's 'Astronomy Picture of the Year 2010'. -- Daniel