Going for the Planets - and getting involved

Communications Homepage for the
Meetings of European Planetary and Cometary Observers
and other pan-European and global planetary amateur activities


Three days to go ... until the first ring plane crossing of Uranus in 42 years!



[April 29, 2007] A largely ignored (except once by the Planetary Society's Blog) but exceedingly rare celestial event is about to commence: For the first time since 1965 Uranus will show the exact edge of its ring system to the Earth on May 2nd. This unusual geometry will repeat twice over the following year, plus Uranus will experience equinox this December. A lot of unique observations will be performed by professional astronomers in a major campaign - and one wonders who much amateurs would be able to contribute. Uranus is clearly resolved by moderate telescopes but little more than the disk is usually imaged (just check out the ALPO image archive for "Uranus" in the last few years, e.g. Sep. 17, 2006).

Perhaps there is a chance to get the epsilon ring as well by clever choice of filters (Uranus specialist I. de Pater recommends 890 nm where a methane absorption band is located; personal mail today), long exposure and the perfect opening angle (see the Keck sequence above for its shrinking 2001 to 2005)? It's well possible that the epsilon ring simply disappears at RPX because of its density and thinness, instead of getting ever brighter because of higher column density. Large telescopes and Adaptive Optics in the Near IR show amazing things, the rings as well as clouds.

Only one thing is certain: You won't get anything if you don't give it a try! E.g. photometric measurements (with CCD or video cameras) of mutual events of the satellites could be possible even with 50-cm telescopes - and there is even an explicit call for amateur involvement in the equinox campaign. A lot has been found out about Uranus in the past, but there is much more to learn - e.g. if the claim that Herschel himself may have spotted the epsilon ring (which leading Uranus ring specialists don't consider credible) could have any merit ...

25 years ago: Venera 13 & 14 on Venus - and my first-ever 'paper'

[March 8, 2007] It was 25 years ago, on March 1 and 5, 1982, that two Soviet spacecraft gently landed on the hot surface of Venus - and sent home the first color images from this world: Venera 13 and Venera 14. These were wide panoramas, obtained with two Viking-like scanner cameras, only that the cameras were tilted half-way towards the ground (one can be seen here on the left side of the spherical s/c body). This allowed them to capture detail all the way to the horizon as well as close the landing spot, all in one big swoop; given the limited survival time, this was a rather clever solution. The resulting panoramas, however, looked quite unnatural to the human eye. Soon after the first versions of the Venera 14 panoramas became available I had an idea! My school had recently obtained its first computer - yes: one computer - for all students to use, an HP 9845A (widely in use at the time, though not in education but in labs). It was not capable of handling greyscale images but had a plotter that could also be used as a clumsy graphics tablet.

And so I went about to 'scan' a newspaper reproduction of one of the Venera 14 panoramas (an old b/w version is shown on top here), clicking on all the corners of the lava blocks lying around. In the end I had 1908 (x,y) coordinates in the database, representing both Venus' surface and s/c details in the image (see middle picture). From the shape of the horizon segments and the general distortion pattern I then estimated a center of geometry, transformed the coordinates and re-plotted them (lower picture; clicking on all makes them bigger). The resulting image reminded me of transformed versions of the Venera 9 and 10 b/w panoramas I had seen in the literature, so the the general procedure seemed to be sound. And thus I wrote, at an age of 17, my very first 'paper', published in Telescopium [Mitteilungen der Volkssternwarte Bonn Astronomische Vereinigung e.V.] 10 #2 [1982] 15. Only in recent years did I finally encounter a few other attempts to to improve the Venera 13/14 images, vastly more sophisticated (scroll way down) than mine a quarter century ago, of course. But they brought back lots of memories - as does the 25-year anniversary of the actual landings now!


How we swung around Mars

Changing course with Rosetta: live from mission control

[Feb. 25, 2007] ESA's comet-bound Rosetta spacecraft made it safely past Mars and through its shadow this morning Central European Time, now heading for a 2nd Earth flyby on Nov. 13. As it is customary for critical interplanetary events, the European Space Operations Centre in Darmstadt, Germany, threw a press event/party on the occasion, as it had done in recent times e.g. for the Mars Orbit Insertion of Mars Express, the arrival of Huygens at Titan or the crash of SMART-1 into the Moon. Until recently the media gathered in a big conference room in ESOC's H building, often decorated in style for the particular mission, but since the SMART-1 event, we have moved 'closer to the action': into the much smaller meeting room E16 directly next to the main control room! Separated from the actual flight controllers just by a glass front, events can be followed probably more closely than with any other space agency, while key managers step in front of the guests to give updates. And so it was again, in the wee hours of Sunday, Feb. 25, 2007.

2:40 CET (1:40 UTC): The ESA Director of Science Programmes, Prof. David Southwood, starts the event with one of his uplifting speeches, reminding everyone (including some dignitaries from the Science Programme Committee in the front row) that it was ESA which first dared to venture really close to a comet, with Giotto 21 years ago. A long hiatus in planetary exploration followed, but with Mars Express, Huygens, SMART-1 and Rosetta "Europe is back firmly in the Solar System". Southwood calls Rosetta "the ultimate mission" in cometary science (not quite true, actually: that would be a sample return which no agency has dared to do so far) - and he states that "I don't have any guilt spending public money" on this kind of fundamental science: "It's a duty" for us, actually.

Next comes the Head of Flight Dynamics, Dr. Uwe Feucht (note that about everyone in charge is from a different country, part of the charm of ESA): He stresses that the Mars flyby is not a gravity assist to gain speed as e.g. New Horizons' Jupiter visit (see entry below). It's only about diverting Rosetta's trajectory (which loses a bit of energy) to reach Earth for the next Earth gravity assist, the 2nd of 3. "To reach the comet, turn left at Mars" thusly is the motto of the whole event! The last trajectory correction was performed on Feb. 9, just 4.55 cm/s: This changed the target point in the B plane (which goes through Mars and is perpendicular to Rosetta's flight path) by 60 km. It is now just 11 km off the perfect point, well within margins, and thus no further TCM has been performed since.

Rosetta Mission Manager Dr. Gerhard Schwehm explains that all science being performed around the flyby is strictly a bonus - but a nice one: On the orbiter the camera OSIRIS (bottom and center images) is on as are ALICE, VIRTIS, the NavCam, a plasma and a radiation monitor. The "prime 'viewing spot'" goes to the Philae lander, however, which has its owns batteries and can thus operate even through closest approach and and Martian shadow ("eclipse") when all orbiter instruments are at sleep! On Philae part of the CIVA camera is operating as well as the ROMAP magnetometer - and the data will be downlinked with priority after the encounter (just after 15:00 CET a truly stunning image has been released indeed; top).

3:03 CET: Rosetta Flight Director Dr. Paolo Ferri confesses that this is "quite a tense moment". Closest approach (at 249 km altitude, with a 3-sigma uncertainty of 3 km, as Feucht had predicted) has already happened in spacecraft event time, but with Mars still nearly on the other side of the Sun, signals take 17 minutes and 33 seconds to reach Earth, thus in ground received time the key events of the flyby are still ahead: loss of signal in 10 minutes when Rosetta disappears behind the Martian limb for 15 minutes, C/A and the eclipse - the first for the mission.

3:14:10 CET: An announcement comes through the mission control voice loop that the S band carrier has been lost - the occultation has begun. Always a somewhat uneasy time. Rosetta Spacecraft Operations Manager Andrea Accomazzo comes in and states that the loss of signal happened right at the predicted time, so the trajectory must be perfect! Rosetta is already in eclipse, and everyone hopes that the batteries work - they were used the last time during launch, ever since Rosetta was in sunlight. Many tests had been done, though, to make sure the batteries are up to the task. If Rosetta had launched as planned in 2003, there would not have been any eclipses, so lots of internal configurations of Rosetta had to be changed for the few critical minutes near Mars. E.g. the onboard software had to be taught not to panic when suddenly the Sun disappeared.

The Head of the Ground Facilities Operations Division Manfred Lugert stresses that not only ESA's own ground stations in Australia and Spain but partners from around the world were involved in getting Rosetta's trajectory right: As with Venus Express the Delta DOR (Delta Differential One-Way Ranging) technology is used in which two widely separated antennae track the spacecraft to triangulate its 3D position in space. And the antennae had to be really big as the signal at Earth is a mere 1/100th of a picowatt. At the moment only ESA's own New Norcia station in Australia is listening for the S band carrier that was kept on (w/o telemetry) "as a lifeline".

3:28:20 CET: Another announcement through the voice loop - the signal is back! Applause in E16. Accomazzo stresses that the reaquisition of the carrier proves that Rosetta is surviving in Mars' shadow. Ten more minutes before it sees the Sun again. In the meantime OSIRIS PI Horst Uwe Keller shows some of the images his camera got during approach: He is particularly excited about detached cloud and/or dust layers 60 km or so above ground (the middle image became available a few hours later). This may already constitute a discovery as it would be hard to explain how dust could get that high in Mars' tenuous atmosphere. For OSIRIS the Mars observations are also about cross-calibration with other Rosetta instruments as well as the HRSC camera on Mars Express. Could OSIRIS have operated at closest approach, it would actually have reached 5 meters ground resolution.

3:40:39 CET: The eclipse has now ended, says another announcement. And the S band carrier is still there, reports Accomazzo, drawing another round of applause. So Rosetta made it: "This was the most critical time since launch," says the Head of the Mission Operations Dept. Dr Manfred Warhaut. And at 3:52:40 CET the stream of telemetry is also back, showing up as a big spike on a spectrum analyzer. Happy faces everywhere, ESA's top managers are almost bubbly with joy and tell all kinds of interesting stories when triggered (but that would be another article :-). In particular Gerhard Schwehm tells me that so far all hardware on Rosetta is performing well, it's only the software in several instruments that needs to be improved. But there is plenty of time (arrival at the comet is only in early to mid-2014), plus four more opportunities for trying out Rosetta's instruments: two more Earth flybys and two asteroid visits. From 2011 til 2014 Rosetta will then hibernate, but even then enough work remains: the complex operations at Churyumov-Gerasimenko have to be prepared. (Clicking on the inlined images takes you to their sources. The upper one is (C) CIVA/Philae/ESA/Rosetta, the other two are (C) 2007 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA.)


Venus back in evening sky - great UV images already

[Feb. 25, 2007] A rather good evening visibility of Venus has begun, and the worldwide Venus archive is growing again: Interesting UV detail has been imaged on the small disk e.g. on Feb. 21 - but the best images I've seen so far were taken Feb. 14 in Austria and Feb. 22 in Germany!


New Horizons approaching Jupiter; many images available, but now just waiting

[Feb. 25, 2007] With NASA's New Horizons spacecraft approaching Jupiter for a much-needed gravity assist on Feb. 28, many raw images from the LORRI long-distance camera from the last few weeks have been made available in near-real time, as well as processed image products. During the hot days, however, hardly any new pictures will become available as everything goes onto internal storage (just as it will be done in 8+ years at 'dwarf planet' Pluto). The mission's PI, however, is blogging about what's going on both on the homepage of New Horizons and at Astronomy.com.


Finally a handful of low-altitude VEX images available

[Nov. 13, 2006] Two of the few new releases were taken in late July at 1.7 and 2.3 µm wavelength and show Venus' cloud structure in more detail than before; they came with a Press Release in October, and there were also some VEX news at the DPS Meeting in Pasadena, reported by the BBC and the Planetary Society. For solar conjuction the s/c was turned off but should be at work again now. Also the one year launch anniversary was marked recently, with the release of more images at 1.7 µm, from September and again July. Stay tuned here for any new material trickling in! From the SMART-1 impact there were hardly any news since two months, by the way. But you can now watch the EuroPlaNet video, parts of which were shot at the Graz meeting this June.


Earlier messages - there was a 2-month hiatus which is now over! - regarding
Europe-wide amateur planetary activities can be found here!