Took a few snaps today in the Mars Express Dedicated Control Room here at ESOC. More are available in the EuroSpaceAgency Flickr account. -- Daniel
I had the chance to ask him how the current Mars Express flyby studies could potentially help Russia's planned Phobos-Grunt ('Phobos soil') sample-return mission, expected in the 2012 timeframe.
His answer was interesting, and the activity will also directly benefit ESA's own Rosetta mission (full info after the jump). -- Daniel
Engineering drawing of Russia's Phobos-Grunt spacecraft
In an email earlier today, ESA's Flight Dynamics team here at ESOC provided their latest Mars Express orbit prediction for tomorrow's Phobos flyby.
It is based on ground station tracking data received up until yesterday, and includes data from the NASA Deep Space Network (DSN) station at Goldstone, California, and from ESA's own Deep Space Antenna (DSA) station at New Norcia. The predicted closest approach time to Phobos remains unchanged at 20:55:40 UTC (21:55:40 CET) on 3 March 2010, with a miss distance of 77 km from the centre of Phobos. This implies that Mars Express will pass 67 km above the surface of Phobos (which has an average radius of 11.1 km).
The prediction also confirms that there will be no occultation by Phobos on 3 March, meaning that Mars Express will not pass 'behind' Phobos as seen from the Earth. There will be a very brief eclipse caused by Phobos passing in front of the Sun (as seen from Mars Express) - in other words, Mars Express will enter the shadow cast by Phobos. Thanks to Frank Budnik for the details! -- Daniel
A few key details gleaned from various sources:
- Planned date/time of closest approach: 3 March 21:55 CET (20:55 GMT)
- Planned altitude above Phobos surface: 67 km
- First planned High Resolution Stereo Camera (HRSC) observations: 7 March, at 107 km altitude
- Phobos shape/size & mass: 27 km × 22 km × 19 km || 1.072 x 1016 kg, or about one-billionth the mass of Earth
- One-way radio signal travel time between Mars Express and ground stations on Earth: 6 minutes, 30 seconds (6:30)
- Straight-line distance between Mars Express and Earth: 116 919 058 620 m = ~116 million km
Will update this post a little later with more... -- Daniel
ESA's Mars Express will skim the surface of Mars' largest moon Phobos on Wednesday evening. Passing by at an altitude of 67 km, precise radio tracking will allow researchers to peer inside the mysterious moon. Latest update is now available in the ESA website. -- Daniel
An excellent overview of orbits in space and featuring "Mars Express and the mystery of Phobos" has just been published in the ESA Kids pages. The folks over at the Kids site do an excellent job of making space science accessible to all ages, and in particular those in the elementary school age bracket. The pages are available in English, German, Spanish, French, Italian and Dutch.
If you know of any up-and-coming space fans, be sure to tell them about Mars Express and Phobos and point them toward the ESA Kids site! -- Daniel
Mars Express is currently working through its series of Phobos flybys, heading for its closest approach on 3 March 2010. Different instruments are used on different flybys to gain different information about the mysterious moon.
ASPERA is studying the interaction between the sleet of electrically charged particles given out by the Sun, called the solar wind, and the surface of Phobos. HRSC will produce high resolution images of surface, paying particular attention to the Phobos-Grunt landing site.
MaRS will determine the Phobos gravity field allowing the internal distribution of mass to be determined. MARSIS is studying the sub-surface of Phobos, seeking indications of structure and internal composition. SPICAM, PFS, OMEGA are characterising the surface of the moon, with PFS aiming to measure the day and night side temperature.
Digital terrain model of Phobos derived from HRSC data. Published in M. Wählisch et al., "A new topographic image atlas of Phobos", Earth Planet. Sci. Lett. (2009), doi:10.1016/j.epsl. 2009.11.003 Credits: ESA/ DLR/ FU Berlin (G. Neukum)
The full list of flybys, altitudes and instruments is as follows:
Date Altitude (km) * Instruments used during flyby
16 February 991 PFS, SPICAM, ASPERA
22 February 574 PFS, SPICAM, ASPERA
25 February 398 PFS, MARSIS
28 February 226 PFS, MARSIS
03 March 50 MaRS, ASPERA
07 March 107 HRSC, OMEGA, MARSIS, SPICAM, ASPERA
10 March 286 HRSC, OMEGA, MARSIS, ASPERA
13 March 476 HRSC, SPICAM, PFS, ASPERA
16 March 662 HRSC, SPICAM, PFS, ASPERA
19 March 848 HRSC, SPICAM, PFS, ASPERA
23 March 1341 Not used
26 March 1304 HRSC, SPICAM, PFS, ASPERA
* Distance from the surface of Phobos
You can read a detailed rundown of the flyby campaign here. -- Stuart
OMEGA Visible and Infrared Mineralogical Mapping Spectrometer on board Mars Express - Credits: ESA
The first of the two radio-sounding proficiency tests (see my earlier blog entry on the critical radio science experiments) was completed in the night from 22/23 Feb, and went very well. The second test is scheduled for tonight (24.02), and if no problems are encountered, then Mars Express is all set for probing the moon's gravity field with unprecedented accuracy.If Phobos really were an ancient space ship of a long forgotten civilization, we could then see how much fuel the former owners of this ancient space asset would have had left, and where the fuel tanks would have been located! :-) (More details after the jump.) -- Hannes
Phobos is doomed. It is gradually spiralling towards Mars and eventually could slam into the planet’s surface, leaving a large crater as its parting gift. Believe it or not, this discovery led to speculation that Phobos could be a space station launched by an advanced Martian civilization.
At the time, calculations showed that the moon’s orbit was decaying at around 5 cm per year which was subsequently shown to be an overestimate. Phobos is in an unusually low orbit around Mars, and so it was thought that this drag could be caused by the upper atmosphere of the planet. Russian astrophysicist Iosif Samuilovich Shklovsky set about calculating whether the atmosphere could indeed be responsible. What he found surprised not only him, but many others too.
For the atmosphere to be responsible, Phobos would have to be hollow, like an Easter Egg. If the moon were solid rock, the atmosphere would have little effect. A hollow moon would be susceptible because it contained so much less mass. But if the moon were hollow, it could not be a natural object.
That's no moon, it's a... no wait, it is a moon.
Credits: ESA/ DLR/ FU Berlin (G. Neukum)
Writing in the Irish Astronomical Journal in 1964, Estonian astronomer Ernst Öpik noted that there were in fact three possible reasons for Phobos’s orbit. The first was that the observations were in error and Phobos was not spiralling inwards. The second was as Shklovsky suggested – and Öpik agreed that if it were hollow then Phobos was artificial. The third suggestion was that Mars’s gravity acted across the moon producing a so-called tidal force, which could rob the moon of energy.
Dr S. Fred Singer, an American physicist, joined forces with Öpik to investigate. Singer doubted the decay rate was as large as 5 cm per year. He was right. Sadly for the UFO enthusiasts, Phobos was found to be decaying at just 1.8 cm per year and this allowed Singer and Öpik to show that the third case is the correct one. Tidal forces are responsible for the moon slowly spiralling downwards. Star Wars fans will remember the classic line from the first movie, “That’s no moon, it’s a space station.” For a while in the 1960s, some astronomers actually thought this might be true about Phobos. -- Stuart
"The Mars Express radio science investigators are hoping that the close approach will provide not only much better estimates of Phobos' mass but also how the mass is distributed within the moon. That is, there appear to be pockets of slightly denser material scattered through Phobos; by passing within 50 km, Mars Express may respond to those differences and the Doppler measurements will reveal where the denser material hides. There is a Mars express radio science group working on Phobos: The radio science PI (Principle Investigator) Martin Paetzold, in Cologne, and Tom Andert in Munich and Pascal Rosenblatt in Brussels who work on the data analysis and interpretation."
I thought his note was interesting in that it shows that (a) planetary radar and radio science can provide exquisitely detailed information on the internal structure of bodies in the Solar System, and (b) it shows the international character of such investigations. Yes, it's an ESA mission doing the closest-ever Phobos flyby and it's a European PI team that primarily conducts radio science (the MaRS team under Martin Pätzold at Köln University), but it's an international set of researchers who follow and keenly support this science.
The interesting thing is, understanding more about Phobos composition and theories of formation is not simply an arcane academic exercise. Phobos may, in fact, play a key role in future human exploration of the Solar System (more details after the jump). -- Daniel
Greetings again to all Phobos and Mars aficionados!
Christian Andreas Doppler (29 November 1803 – 17 March 1853)
The closest-ever flyby of Phobos to date will be dedicated to an experimental method called 'radio sounding'. The way radio sounding works is that we place the object (think a celestial body) we want to investigate close to the trajectory of a moving vehicle (think a spacecraft) equipped with a very stable and precise radio transmitter. We also need a very sensitive receiver equipped with measurement devices to record the received signal (think ground stations). The transmitter on the moving vehicle sends out a continuous unmodulated signal (meaning no actual data will be transmitted - just an 'empty' carrier signal). The receiver receives the signal and then sends that signal to the measurement equipment, which will record the famous Doppler shift of the received signal's frequency (access more details under the 'Full story' link below) -- Hannes.
The American space agency's giant 70m station at Robledo, Spain (DSS-63), will be enlisted to track ESA's Mars Express during Phobos flyby to record extremely precise Doppler data - which in turn will enable Mars Express scientists to obtain the best-ever measurements of Phobos gravity and hence mass (click on 'Full story' for more details). -- Daniel
If you were to stand on the surface of the Red Planet, Phobos would rise in the west. It would appear about one-third the apparent size of our Moon as seen from Earth’s surface, and it would cross the Martian sky against the flow of the other celestial objects before setting in the east. What makes Phobos so different?
Simple: it orbits unusually close to Mars, at an average altitude of around 9400 km (compared with our Moon’s distance from Earth of around 385 000 km). To maintain such a low orbit, Phobos has to move so quickly that it out-paces the planet’s rotation. Mars rotates once ever 24 hours 37 minutes, whereas Phobos completes an orbit in just 7 hours 39 minutes.
Hence, Phobos is constantly overtaking the surface of the planet. All other natural celestial objects, including Mars’s second moon Deimos, are moving more slowly in relation to the surface of the planet and so are brought into view as the surface turns to face them. This causes them to rise in the east and set in the west.
From Earth, only artificial space-borne objects, such as the International Space Station, are in such low orbits and travelling so fast that they appear to rise in the west.
Back on Mars, the Phobos weirdness does not stop with its backward journey through the sky. Because the moon is in such a low orbit above the equator, it can never be seen from inside the Martian polar circles. -- Stuart
Good morning from the Mars Express Dedicated Control Room (DCR) at ESA/ESOC!
Yesterday's orbit change manoeuvre went as planned, and this morning at 05:52 UTC (06:52 CET) we passed by Phobos at a predicted altitude of 991 km, the first in our series of 12 planned flybys. This pass was used to acquire PFS spectrometer readings and to scan the moon with our MARSIS subsurface sounding radar.
As I write these lines, data from this exciting event is being downloaded from Mars Express via NASA's DSN trackign station at Goldstone, in California's Mojave dessert, and we are all anxiously awaiting the analysis by the flight dynamics experts at ESOC to show the actual, observed fly-by parameters.
Stand by for more exciting news about our visits to a moon that has so far provided us with many more questions than answers. -- Hannes
PS: Read today's full report in the ESA website: