Mars Express Blog

Mars Express Blog http://webservices.esa.int/blog/blog/7 Mars Express is Europe’s first planetary mission. At launch, the mission consisted of an orbiter carrying seven instruments for remote sensing observations of the planet, and a lander (Beagle 2) for on-the-spot measurements of Martian rock and soil. Mars Express started science observations at the Red Planet in January 2004, and since then it has been delivering an incredible amount of scientific results. The ‘Express’ part of the name highlights the fact that the spacecraft was built more quickly than any other comparable planetary mission. In fact, it took only five years from mission approval to launch. In addition to global studies of the surface, subsurface and atmosphere of Mars with unprecedented spatial and spectral resolution, the unifying theme of the Mars Express mission from orbit is the search for water in its various states, everywhere on the planet by all its seven instruments using different techniques. danielscuka 2012-02-10T10:21:43Z Farewell to Phobos (for now anyway) http://webservices.esa.int/blog/post/7/1090 As this particular Phobos flyby season comes to an end, I caught up with Michel Denis, spacecraft operations manager; Nicolas Altobelli, scientist with the science ground segment; and Olivier Witasse, project scientist, to ask how it all went and what we can look forward to in the future. -- Stuart <img src="http://www.esa.int/images/6_7926_phobos_nadir_large,0.jpg" width="300" height="248" align="left" />This has been the most ambitious Phobos flyby campaign yet attempted, how did it go? Michel Denis: “After almost 8000 orbits which have all been a bit different from each other, and after about 10 Phobos campaigns, we had mixed feelings between the old-sailor's confidence "it will be all-right, we have mastered much more complex activities already" and the juvenile excitement of the beginners "it's so close, and we must turn the spacecraft swiftly, and what happens if...?" <table cellpadding="0" cellspacing="0"> <tbody> <tr> <td style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 13px"> Credits: ESA/DLR/FU Berlin (G. Neukum)  </td> </tr> </tbody></table>Both were true. After all it was just another couple of observations, well prepared like all the others thanks to well known processes, proven tools and above all the expertise of the people. Still, a few things were special in the way Mars Express was used, and a few minor events happened that forced a few individuals to react within a few hours, in order to recover a plan that had been agreed for months by a wide community. In such cases, it's good to be as flexible as the youngsters and as experienced as the old sailors. The most well known example is that the orbit manoeuvre required to prepare the Phobos encounter, slightly over-performed by a fraction of a percent, which is completely normal and not an issue under other circumstances. But here, due to bad luck, this small overshoot slightly increased the orbital period. It would have meant Mars Express arriving a few seconds later at the closest approach on March 3rd.  Again, this would not be a big deal in principle but, in this specific planetary configuration, Phobos would have hidden the Earth and made most of the long-planned radio-science observation inoperable. To avoid this undesired alignment, in just a few hours the Flight Dynamics experts invented a clever strategy, and minor additional orbital offsets were commanded to the spacecraft within the few days remaining before closest approach. In the control room, during the closest flyby, we were very confident and slightly anxious at the same time. As predicted, thanks to the small correction no occultation occurred and the radio-science experiment was a complete success. A less obvious but also important concern was raised a few weeks later by a ground station failure. This is an also rare but possible anomaly, and it happened just at the time when Mars Express was sending the data from one of the Phobos pictures taken by HRSC to Earth. Such data losses are covered by our procedures and we have memory space onboard to temporarily store missed data and resend it to Earth later. In this case though, the ground anomaly lasted for more than an hour and affected the HRSC data return containing the Phobos picture, which would soon be overwritten by other observations. The special extra space onboard was too small to secure the Phobos picture. So we had to copy the HRSC data to the large storage area normally reserved for another instrument.  That instrument was also in use but producing less data. Then we had to bring all the data back to Earth without affecting the data from the other instrument. Mission accomplished.” Nicolas Altobelli: This season has been indeed quite intensive in terms or preparation, in particular because we had a couple of the closest flybys ever attempted. The timing and geometry of the observations therefore had to be planned with a precision not usually required for 'routine' observations of the martian surface. This demanded a perfect flow of information between the instrument teams, external to ESA, the science planning centre at ESAC in Spain, and the spacecraft flight control team at ESOC, Germany. Fortunately, things went quite well overall. In particular, the flyby with closest approach provided unique data to the radio science gravity experiment. The HRSC camera obtained high-resolution pictures and the MARSIS instrument recorded radar echoes of Phobos. After analysis these combined data will hopefully provide an incremental step in constraining Phobos’ physical properties and possibly give hints as to its origin."  Did you have to use Mars Express in an unusual way to make this happen? Michel Denis: "Mars Express is permanently used in special ways, because the mission profile evolves due to changing environmental factors, like the distances to the Sun and Earth, the eclipses, the seasons and even local time on Mars. The spacecraft has to cope with high and diverse mission ambitions. It has to be able to take 3D pictures, make atmospheric studies, perform mineralogy and radio experiments, both in routine coverage and targeted campaigns. It must deal with constraints that the planners have to respect all the time, such as the fact that all the instruments are fixed, power is limited, data stores are limited, and so on. For this particular Phobos campaign we simply used several of the special but already validated configurations. A few elements were new though: the Phobos tracking slews for optical observation at short distances, when the spacecraft was turned at a rate twice as fast as the usual speed limit. In a car you can do this only if you are on a special circuit and with the proper authorisations, and this is exactly what we had. Also unique was the combination of the Phobos campaign with a series of major orbital change manoeuvres, which allowed Mars Express to go very close to Phobos, while shifting it to an orbit more favourable to the optical instruments for the next few years. Even more challenging than these settings that we had long known about and prepared for, were the situations that the events asked us to handle. Here we had again this wonderful ‘Mars Express feeling’ that we have experienced so many times since the launch in 2003.” When can we expect to hear the science results? Olivier Witasse: "We have already published he first images, data from the gravity experiment and echoes from the radar, all on the web portal of the European Space Agency and on this blog. All the teams are very busy doing the data analysis. Results will be discussed amongst the team members, and at a Science Working Team meeting to be held in June, between all the Mars Express experiment teams. This is going to be exciting. Then, it is planned to share the results and their interpretations with the scientific community at two major events: the European Planetary Science Congress (Rome, September) and a workshop at IKI, Moscow, in October, on the Phobos-Grunt mission. I expect some articles to be published later in the year. The papers always take time." When will Mars Express next encounter Phobos? Nicolas Altobelli: "Mars Express' highly eccentric orbit crosses Phobos’ orbit periodically as a consequence of the natural drift of the pericentre latitude. This is induced by the non spherical martian gravity field. However, the spacecraft position on its orbit must be fine-tuned in order to 'catch' Phobos at the right time. Close encounters below 200 km distance will be possible again in early 2011." What will Mars Express do in the meantime? Nicolas Altobelli: "Mars Express will go back to its very busy scientific observation schedule, primarily dedicated to the observation of Mars. As usual, the Science Ground Segment at ESAC will aim at building observation plans, in collaboration with the science teams and the project scientist, in order to collect data sets on the atmosphere, surface and sub-surface of the red planet." Olivier Witasse: "We have some clear scientific objectives planned until end of 2012, and we’ll make sure that we achieve them."   General Phobos Fly-By 2010 2010-03-31T15:59:34Z stuartclark What's next for Phobos exploration? http://webservices.esa.int/blog/post/7/1084 <a id="res_12825" href="http://webservices.esa.int/blog/gallery/7/Mars-Express_Phobos_orbits.jpg"> <div style="text-align: center"> <img src="http://webservices.esa.int/blog/gallery/7/previews-med/Mars-Express_Phobos_orbits.gif" border="0" alt="Date: 15 Feb 2010 Satellite: Mars Express Depicts: Diagram of the Mars Express and Phobos orbits Copyright: ESA On 3 March 2010, Mars Express performs its closest flyby ever of Mars' innermost moon Phobos. This diagram shows the orbits of Phobos and Mars Express around Mars, with the point where the orbits cross indicated at top left. The orbit of Phobos lies virtually in Mars' equatorial plane and is indicated in yellow. Mars Express is in a polar orbit. Several revolutions are depicted here, with the colour indicating the parts that are over the northern hemisphere (white) and the southern hemisphere (blue) of Mars. Because the orbit of Mars Express evolves, with the line of apsides drifting, sequential revolutions do not overlap." /> </div> </a> With today's flyby at 12:17 UTC (13:17 CET), the current Phobos flyby campaign will be complete. Given the present polar and elliptical orbit of Mars Express (meaning that it orbits over the Red Planet's North and South poles and varies in altitude from fairly close to quite far away), and the near-circular and equatorial orbit of Phobos, encounters between the bodies can be expected every five months. However, the number of flybys, the geometry and the closest distances are always different. The current campaign was unique: It stands out with a total of 12 fly-bys (more than any campaign before) and a minimum approach distance of 77 km from the centre of the moon, which corresponds to approx. 67 km from the surface (the closest flyby of any spacecraft to date). So, what about the next campaigns? Let's look ahead to the next two flyby 'seasons.' The next one will come in August 2010, with nine flybys within 1200 km from Phobos. The closest approach will be about 403 km over Phobos' night side, on 24 August 2010. Then, between December 2010 and January 2011, 10 flybys are planned, with the closest one coming within 96 km of the moon's dayside, on 9 January 2011. (This is, by the way, roughly four weeks before Mars passes behind the Sun (as seen from Earth), and only a few days before Mars Express science operations will stop for approximately 6 weeks due to this so-called 'Solar conjunction'.) Quite interesting observations can be made from such distances indeed! The powerful cameras, spectrometers and other instruments on Mars Express can glean amazing details; repeated flybys will augment coverage of the surface of Phobos, help confirm or improve previous findings, complement existing data sets, and possibly even make new discoveries. So we hope you'll stay with us as we set out to explore this mysterious, small world even further. This month's closest-ever flyby lies behind us, but the excitement is far from over. On the contrary, it has only just begun! - Hannes Griebel and Olivier Witassse General Phobos Fly-By 2010 Science 2010-03-26T20:55:28Z hagriebel First look at the MARSIS radar data for Phobos http://webservices.esa.int/blog/post/7/1082  I have just received the following information from Andrea Cicchetti of the MARSIS radar team. Congratulations to all of those involved; I look forward to the full analysis. -- StuartMARSIS, the radar aboard the Mars Express orbiter, has successfully observed Phobos again. MARSIS is a multi-frequency, synthetic aperture, orbital sounding radar that operates in the range 1.3-5.5 MHz with a 1 MHz bandwidth.The closest flyby in which MARSIS operated during this fruitful Phobos season took place on March 7th 2010, during the 7915th orbit of Mars Express, when the orbiter reached a minimum distance from the surface of Phobos of about 112 km. For instrument safety reasons, the radar software blocks operations when the target is closer than 240 km. Therefore the team had to devise a new set-up of the main navigation parameters, allowing them to reduce the minimum operational distance down to 175 km, while maintaining a high level of safety for the instrument’s hardware.During this flyby, MARSIS successfully collected 6478 echoes from Phobos in just 72 seconds. The carrier frequency was centred at 4.0 MHz with a 1 MHz bandwidth. Taking advantage of the instrument’s internal mass-memory facility, it was possible to store and then downlink the raw unprocessed echoes.  <img src="http://webservices.esa.int/blog/gallery/7/MARSIS%20Phobos%20Flyby%2007-mar-10.jpg" width="480" height="360" /> Credit: ESA and MARSIS team. After the ground-processing of science data, it was found that the radar worked successfully during the flyby. The figure above shows echoes reflected by Phobos as the highest peak in the signal, clearly above the noise level. Scientific analysis of the results is still ongoing. The main quest is the determination of the origin of detected echoes: are they reflections from various surface features of Phobos, or have they been produced by the internal structure of the moon?The MARSIS radar was originally designed solely for the observation of Mars. However, thanks to the Italian operations team, working in collaboration with the international instrument science team, it was possible to re-configure it to allow the observation of Mars’ moon Phobos, a unique target, thereby expanding the scientific capabilities of the mission.In the first phase of the data analysis, the main goal was to validate a new operative configuration of the onboard software and hardware. The scientific analysis of existing and future data will provide us with new and unique insights on the nature of Phobos’ interior.Andrea CicchettiFor the MARSIS Team   General Phobos Fly-By 2010 Science 2010-03-22T15:16:01Z stuartclark So you think it is easy to fly a space mission? http://webservices.esa.int/blog/post/7/1076 Of course you don’t, but this latest post will give you a great ‘behind the scenes’ read about the Mars Express mission. In particular, it highlights the role played by the Science Ground Segment at The European Space Astronomy Centre (ESAC) during the Phobos flyby season. It is their job to make sure that the observations requested by the scientists are possible and then to ensure that they are performed. My thanks go to Nicolas Altobelli and Alejandro Cardesin for taking the time to put this together. -- StuartGeneric role of Science Ground Segment and the Science Operations Centre:The Science Operations Centre (SOC) is part of the Science Ground Segment (SGS) of the Mars Express mission and is located near Madrid, in Villanueva de la Canada. It provides scientific and technical co-ordination between the instrument teams and the Mission Operation Centre (MOC) located at the European Space Operations Centre (ESOC) in Germany. The SOC is composed of a core team of four scientists and engineers working with the support of a broad group of experts on software, technical and various scientific topics, all of them within the Solar System Science Operations Division. The main objective of the whole SGS is to co-ordinate the scientific observation requests from the Mars Express instrument teams and to build the final observation plan that fits in terms of available spacecraft resources (mainly battery power, data rate and downlink capacity). Among other tasks, SGS is responsible for defining the final pointing of the spacecraft and planning the operation of the payloads. These planning activities are performed three months in advance to allow the resolution of scientific and technical conflicts. Should two instruments wish to observe in two different directions, obviously they cannot be operated at the same time, and one has to defer to the other.The SGS also helps teams convert their high-level scientific requirements into geometrical constraints and compute the required spacecraft attitude and associated timings. This latter activity is called Opportunity Analysis and answers the question: When is What feasible and How? <img src="http://webservices.esa.int/blog/gallery/7/MEX_Timeline_with_bullets2.png" width="480" height="360" align="middle" />Diagrams like this show the Mars Express team exactly what the spacecraft is doing.  In a sense, if the MOC can be considered as the skipper of a boat, who pays attention to the 'steering' (spacecraft trajectory control) and the general boat maintenance (fuel available, general health of components...), the SGS can be seen as the navigator and sailor, indicating the directions to follow (spacecraft attitude), looking at all the weather and environmental conditions (planet and spacecraft ephemeris, solar flux, martian season, etc) and carefully taking care of the needs of the passengers (scientific teams) and relying on the rest of the crew (technical experts). As it is not always possible to satisfy all the passengers at the same time, the SGS will receive instructions from the Project Scientist to prioritise the requests. Phobos specialsThe Mars Express spacecraft is on a highly inclined and eccentric orbit aroundMars and periodically crosses Phobos’ equatorial and nearly circular orbit. With a slight offset of the spacecraft position on its orbit, performed by the Flight Dynamics Team at ESOC, the spacecraft can make multiple close Phobos encounters. During this period of time, called the 'Phobos Flyby Season', the routine co-ordination task of the SGS becomes more hectic.Co-ordination meetings and teleconferences are set up between the instrument teams and the SGS to collect special requirements that have to be applied during the flyby measurements. The SGS provides a detailed geometrical description of the events, relevant for any type of experiment performed. These include the minimum approach distance, the solar phase angle value (which determines the illumination conditions), the spacecraft velocity profile, whether Phobos will be in Mars' shadow, whether an occultation of radio links is expected. In addition to the geometrical studies, the SGS performs an estimate of the spacecraft resources that will be needed by the experiments, and judges the overall feasibility of the observation plan before sending it to MOC for implementation.Because the precise position of the spacecraft on its orbit cannot be known to any high precision (within 1 second) until a few days before the Phobos flybys, the SGS co-ordinates specific observation requests from the High Resolution Stereo Camera (HRSC) directly with Flight Dynamics. For example, when the spacecraft gets very close to Phobos, (say 100 km), the high relative velocity would smear the images and so this must be compensated by spacecraft motion (slews). A complicated slew pattern is computed by the HRSC team and communicated to Flight Dynamics, who will make certain that it is executed in a timely manner by the spacecraft, using the latest orbital determination result. The SGS supervises this information exchange and ensures that the instrument commanding will stay in line with the final spacecraft orientation strategy. Nicolas Altobelli, Alejandro Cardesin   General Phobos Fly-By 2010 Science 2010-03-18T11:53:56Z stuartclark Phobos on Astronomy Picture of the Day http://webservices.esa.int/blog/post/7/1074 We’re all thrilled to see the Phobos image from the 10 March Mars Express flyby featured on the Astronomy Picture of the Day website today.  Even if you saw the image yesterday, do go and have a look, the APOD team have provided an excellent set of links in the caption for you to explore more about the mysterious origin of Phobos. Check it out <a href="http://apod.nasa.gov/apod/ap100317.html" target="_blank">here</a>. -- Stuart  General Phobos Fly-By 2010 2010-03-17T12:41:56Z stuartclark New Phobos images sent in by HRSC team http://webservices.esa.int/blog/post/7/1073 The Mars Express HRSC team sent in a pair of new images earlier today based on imagery acquired on 10 March 2010. (Click on images to access full-size versions.) -- Daniel   <div style="text-align: center"> <a href="http://www.esa.int/images/6_7926_phobos_nadir.tif" target="_blank"><img src="http://www.esa.int/images/6_7926_phobos_nadir_large,0.jpg" border="1" width="400" height="331" /></a> </div>   Phobos as seen by the HRSC nadir channel during Mars Express Orbit 7926. This image was enhanced photometrically to better bring out features in the less-illuminated part. Resolution: about 9 metres/pixel. Credits: ESA/DLR/FU Berlin (G. Neukum)    <a href="http://www.esa.int/images/7_7926_phobos_anaglyph.tif" target="_blank"><img src="http://www.esa.int/images/7_7926_phobos_anaglyph_large,0.jpg" border="1" width="400" height="341" align="middle" /></a> The High Resolution Stereo Camera (HRSC) on board the ESA spacecraft Mars Express took the images for this 3D stereo composite of the surface of the moon Phobos on 10 March 2010. The image data were taken from a distance of 278 km with a spatial resolution of about 9 m/pixel in orbit 7926. All images are contrast-enhanced and geometrically adjusted for flight movements. The anaglyph has also been slightly geometrically adjusted at the left rim of the Phobos image to correct for viewing conditions. Credits: ESA/DLR/FU Berlin (G. Neukum)   Phobos Fly-By 2010 Science 2010-03-16T14:42:52Z danielscuka Phobos flyby animations - HRSC http://webservices.esa.int/blog/post/7/1071 A pair of excellent animations sent in by the HRSC team showing the Phobos flyby on 3 March 2010. The first shows Mars Express on its closest-approach orbit, with first Mars than Phobos passing below. The second is an overview showing the relative orbit orientations of Mars, Phobos and Mars Express on 3 March (first animation is below; click on 'Full story' for second...). -- Daniel Copyright: ESA/DLR/FU Berlin (G. Neukum) - Credit: S. Walter/Celestia/NAIF/SPICE   <iframe align="middle" frameborder="0" height="400" scrolling="no" src="http://esa-mm.esa.int/multimedia/esoc/hrsc_flyby_videos.html" width="100%"></iframe>     <iframe align="middle" frameborder="0" height="400" scrolling="no" src="http://esa-mm.esa.int/multimedia/esoc/hrsc_flyby_videos2.html" width="100%"></iframe> Copyright: ESA/DLR/FU Berlin (G. Neukum) - Credit: S. Walter/Celestia/NAIF/SPICE Phobos Fly-By 2010 2010-03-15T12:28:46Z danielscuka HRSC images of Phobos now online http://webservices.esa.int/blog/post/7/1070 The Mars Express High Resolution Stereo Camera (HRSC) <a href="http://www.esa.int/SPECIALS/Mars_Express/SEMK17CKP6G_0.html" target="_blank">flyby images have just been published in the ESA web portal</a>. Access the full article & images plus very cool animations provided by the HRSC team... -- Daniel     Phobos Fly-By 2010 Science 2010-03-15T12:01:58Z danielscuka Phobos image update http://webservices.esa.int/blog/post/7/1067 Just wanted to keep you all informed. The camera team are busy processing the flyby images. We'll be posting them as soon as we have them. Stay tuned! -- Stuart  General Phobos Fly-By 2010 2010-03-11T16:38:09Z stuartclark Preliminary radio science results just in http://webservices.esa.int/blog/post/7/1065 Just had the following message through from Mars Express Project Scientist Olivier Witasse. -- Stuart“The Mars Express Radio-Science team, led by Martin Pätzold (Cologne University), has performed a preliminary analysis of the radiometric data recorded during the evening of closest approach, 3 March 2010. The NASA ground-station DSS-63 near Madrid recorded the frequency of the transmitted signal, at about 8.4 GHz and 2.3 GHz, which contains the signature of Phobos’ gravity field. To be able to decipher this weak signature, the team has subtracted all known variations, which would have been measured even in the absence of Phobos. What remains is produced by the gravity of Phobos pulling Mars Express.  <img src="http://webservices.esa.int/blog/gallery/7/First_residuals_detrended-1.gif" width="400" height="300" align="left" />                        Credit: ESA/ Department of Planetary Research at the University of Cologne (M. Pätzold).  The grey line in the image shows the frequency change due to Phobos during a 20-minute window, centred on the closest approach. Before closest approach, the effect of Phobos on the spacecraft is negligible. Then there is a clear jump in frequency at closest approach. This is Phobos slightly changing the orbit of Mars Express. The blue line is the expected frequency change assuming the mass of Phobos, as measured during a previous flyby, is evenly distributed throughout the moon’s interior. There are clearly small differences between the blue and grey lines. The challenge now for the Radio-Science team is to dig into these small differences to prise out information on the mass distribution. “The real work starts right here,” says Pätzold.“It may take a few weeks for the extraction of precise information on the interior of Phobos,” says Tom Andert, from Munich University.The Mars Express close encounter with Phobos was also observed by three European VLBI network stations: the 20 m Wettzell radio telescope (Bundesamt für Kartographie und Geodäsie, Forschungseinrichtung Satellitengeodäsie, Germany), the 14 m Metsähovi (Aalto University - School of Science and Technology, Finland), and 40 m Yebes (Observatorio Astronómico Nacional, Instituto Geográfico Nacional, Spain). Data processing was performed at the Metsähovi Radio Observatory, and analysis at the Joint Institute for VLBI in Europe (The Netherlands). <img src="http://webservices.esa.int/blog/gallery/7/12528-Plot_Track.gif" width="480" height="250" align="left" />                     The residual Doppler frequency pattern, as detected by the Wettzell radio telescope is shown on the plot. The sharp swing of the carrier line frequency at 21:03 UT corresponds to the closest proximity of MEx spacecraft to Phobos. The people who contributed to this project are Guifre Molera Calves and Jan Wagner (MRO, Finland), Gerhard Kronschnabl (BKG, Germany), Pablo de Vicente (OAN-IGN, Spain), and Sergei Pogrebenko (JIVE, The Netherlands).   General Phobos Fly-By 2010 Science 2010-03-09T15:15:59Z stuartclark