|
|
The Planetary Society Blog
By Emily Lakdawalla
Rosetta update
Feb. 20, 2007 | 10:52 PST | 18:52 UTC
Rosetta is fast bearing down on Mars. As of this writing it's only about 3 million kilometers away, zooming toward a 250-kilometer flyby. Last week I lamented my inability to find much information on Rosetta's science plans. A lot of people sent helpful emails -- thanks! -- and, on top of that, I now have in my possession several science planning documents for the flyby! It will take me a couple more days to wrap my head around what all the acronyms and abbreviations mean, but I will shortly have a science timeline for the Rosetta Mars flyby ready for your enjoyment, much like the one I wrote for New Horizons' Jupiter flyby.
These documents will make interesting reading, but I've got even better news for you: The Planetary Society is sending Doug Ellison, host of unmannedspaceflight.com, to Darmstadt, Germany, for the flyby. Doug will be reporting in this space beginning on Saturday, the 24th, giving you frequent updates on the status of the spacecraft, and keeping you posted with images and news as they become available. (Poor Doug: the flyby occurs at 3 in the morning, Central European time. I suspect it'll be mostly an American audience that will be watching the events live -- you Europeans will have to decide whether you'll be staying up late or getting up early!)
Rosetta is not yet conducting science operations. For reasons of spacecraft health, it is only allowed to spend about four hours doing science before Mars closest approach, so that will begin on February 24 at 18:00 UTC (10:00 PST) and continue until 22:10, when Rosetta has to shut its science instruments down for the perilous passage through Mars' shadow. Closest approach will happen on February 25 at 01:54 (Feb 24 at 17:54 PST). Here's one diagram taken from the science planning documents I'm working with, to whet your appetite. It shows the angular diameters of Mars, Phobos, and Deimos as seen from Rosetta during the flyby. I've added on boxes (green) showing when the spacecraft will actually be doing science, and horizontal lines (white) to show the fields of view and angular resolutions of the two instruments on the main camera system, OSIRIS. [NOTE: An earlier version of this diagram had the resolutions plotted incorrectly. I've now fixed the error.] Angular diameters of Mars, Phobos, and Deimos from Rosetta (annotated)This diagram indicates the angular diameter, in degrees, of Mars (blue), Phobos (pink), and Deimos (yellow) as Rosetta passes by the Mars system on February 24 and 25, 2007. Green boxes indicate the periods before and after closest approach ("CA") during which Rosetta will conduct science observations. Horizontal white lines indicate the angular fields of view and resolutions of the OSIRIS wide-angle and narrow-angle cameras. Credit: Rosetta Science Operations Centre at ESA / Emily Lakdawalla |
Some things you can learn from this diagram:- Mars will fill the narrow-angle camera field of view beginning five hours before closest approach, and will continue to loom that large until five hours after.
- In fact, Mars will fill the wide-angle camera field of view when science observations begin after closest approach. During this time, Mars will be a crescent -- it should be a dramatic view!
- Phobos and Deimos are near the resolution limit for the wide-angle camera, but the narrow-angle camera should be able to get many-pixel views of both tiny moons throughout the period of time shown on this diagram.
For those of you who like multimedia stuff, ESA has just posted a Vodcast update on the upcoming flyby.
|
|
[ what is this? ]