Huygens and data delays
Jan. 13th, 2005 07:36 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
mmcirvinThe Huygens probe is going to fall on Titan early tomorrow morning (Eastern US time). It's usually referred to as a probe rather than a lander, because even if everything goes perfectly from an engineering perspective, it may or may not survive hitting the surface (which is supposed to happen at somewhere around 20 kilometers per hour, enough to seriously rearrange your car). Even if it does, it's only got about half an hour on the surface before the Cassini Saturn orbiter (which is its data relay to Earth) sets beneath the horizon, so that is the absolute upper limit of its useful lifetime. It's going to be a busy few hours.
Huygens is mostly a European Space Agency project, and ESA has historically been less open than NASA about releasing images over the Internet in vast heaps. So the reports that images were not going to be available until several hours after Huygens' atmospheric entry sparked a bunch of complaints on the Bad Astronomy board about ESA being up to its old tricks.
The Space Review article they're referring to is fairly reasonable. It's unreasonable, though, to expect anything close to real-time coverage; the reasons for the delay are primarily engineering-related. Comparisons with Voyagers 1 and 2 are unfair, because Voyager was physically capable of streaming data continuously through its high-gain antenna while taking pictures with its swiveling scan platform; the light travel time to Earth was the major delay. In the case of Huygens, it will be relaying data continuously to the Cassini spacecraft, which has to store it all in something sort of like flash memory, turn toward Earth after the Huygens mission is definitely over, then relay the lot. It would have been prohibitively difficult to put a high-gain transmitter and antenna capable of contacting Earth directly on Huygens. It's hard enough just getting the data to Cassini: had a design error not been caught in time to modify the mission plan, it might have been entirely impossible.
Emily Lakdawalla of the Planetary Society is blogging the Huygens descent from Darmstadt and promises to have any pictures up as soon as they are available, which will be sometime in the afternoon EST.
(Article edited for accuracy...)
Huygens is mostly a European Space Agency project, and ESA has historically been less open than NASA about releasing images over the Internet in vast heaps. So the reports that images were not going to be available until several hours after Huygens' atmospheric entry sparked a bunch of complaints on the Bad Astronomy board about ESA being up to its old tricks.
The Space Review article they're referring to is fairly reasonable. It's unreasonable, though, to expect anything close to real-time coverage; the reasons for the delay are primarily engineering-related. Comparisons with Voyagers 1 and 2 are unfair, because Voyager was physically capable of streaming data continuously through its high-gain antenna while taking pictures with its swiveling scan platform; the light travel time to Earth was the major delay. In the case of Huygens, it will be relaying data continuously to the Cassini spacecraft, which has to store it all in something sort of like flash memory, turn toward Earth after the Huygens mission is definitely over, then relay the lot. It would have been prohibitively difficult to put a high-gain transmitter and antenna capable of contacting Earth directly on Huygens. It's hard enough just getting the data to Cassini: had a design error not been caught in time to modify the mission plan, it might have been entirely impossible.
Emily Lakdawalla of the Planetary Society is blogging the Huygens descent from Darmstadt and promises to have any pictures up as soon as they are available, which will be sometime in the afternoon EST.
(Article edited for accuracy...)