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