[X] My Assistant

[Wyl2006]

I am wondering about two special things:


1. Why was the Imager system of Cassini not set on a scan platform? I am really wondering that more than the half possibilites for RADAR-cartography are lost to do other experiments? This seems not an excellent technical solution.

2. Why was the Huygens camera build with such bad resolution? Also the "test images" done at the LPI parking area would give a lot of questions if people were not said that these things in the picture are trees.

Some experiments with a simple CCD-camera at 1/1000 of the illumination given on Earth shows clearly that better pictures could be done without problems, and there are better compression algorithms.

As the soviet space probe has shown during the 70s and 80s, it is possible to make panorama photos from a torrent surface during a flyby of the bus without serios problems.

I am really wondering on those funny self beloving of some ESA-"professionals" and the things told about these bunch of lousy photos they have gotten.

Some experiments with a simple CCD-camera at 1/1000 of the illumination given on Earth shows clearly that better pictures could be done without major problems.

I am working on that topic making cameras for supervision and examination for night and day.

Greetings: Wyl

[The Messenger]

What is really sad, is no one anticipated the long life of Huygens on the surface:

Hello Huygens, ya, this is Cassini, Aw got nothin but goose eggs on ma '"A" Channel reciever, would you flop what you'all got left on 'A' Channel over to 'B', and resend all you can until you fade?

[ugordan]

What is really sad, is no one anticipated the long life of Huygens on the surface:

First, Huygens was an atmospheric probe. Anything sent back from the surface would be merely bonus science.
Second, the impact speed was not trivial at all and it was uncertain whether the probe would ever survive it.
Third, it was probably seriously considered back then that Titan's surface might be covered with oceans/lakes of liquid methane. There was a distinct probability the probe would land into liquid. If this were to happen, the probe's on-surface life would most likely be reduced to only a few minutes as the criogenically cool methane freezed the probe to death.

From an engineering point of view, it was unrealistic to prepare for an extended surface mission, given also the fact that no great scientific benefit would result from greatly prolonged surface life.
If, on the other hand, they anticipated (and prepared for) the probe's survival and instead it crashed, some people would get a nice new reason to bash ESA on a failed "lander".

[The Messenger]

From an engineering point of view, it was unrealistic to prepare for an extended surface mission, given also the fact that no great scientific benefit would result from greatly prolonged surface life.
If, on the other hand, they anticipated (and prepared for) the probe's survival and instead it crashed, some people would get a nice new reason to bash ESA on a failed "lander".

I don't agree. If you follow the Cassini Event logs, They have recently added programming that allows retransmitting of critical data in the event of a lose during transmission. During T-13, an ultrastable clocking system on one channel switched off, and much of the close-pass data would have been lost if Cassini engineers had not planned for this contingency. This was not an expensive programming change in terms of computer resources and real estate, just thoughful acceptance of the fact that seemingly unnecessary redundancy is a virtue.

There is no doubt this decision was prompted by the transmission failure during T-7(?), and also influenced by the loss of data from Huygens. In the case of Huygens, no, they did not have big enough buffers to retransmit all of the data, but they did have a seven year flight, during which they had plenty of time to contemplate contigencies; and they did know after changing the deployment scheme there may be more ground time. Retransmitting critical data, even if it the original data was fully redundant, would have been a very cheap safety play. So what if Cassini wasn't even listening? And speaking of not listening, my clients and servers do an automatic cycle reset when they don't see any valid data within a specified time out period before giving up. Why was Cassini so dumb?

Finally, if the ESA would not have revealed the loss of channel A data, would the Cassini team have taken the time to plan for such a contigency during T-13? What lessons are there to learn buried in the secret report of the DART debunkle? Let there be light.

[ugordan]

If you follow the Cassini Event logs, They have recently added programming that allows retransmitting of critical data in the event of a lose during transmission.

Recently? Not a chance. They had this ability from the start. This was more of a mission requirement than a contingency capability. That's the sort of contingency used for example when there's heavy rain over the DSN station and the data doesn't all come down in one piece. It had nothing to do with either Huygens or T-7. Cassini's SSR has two pointers, a record pointer and playback pointer. The two can be moved around to accomodate various changes. That's an oversimplification, but you get the point. Read Emily's blog on the recent anomaly.

There is no doubt this decision was prompted by the transmission failure during T-7(?), and also influenced by the loss of data from Huygens.

As I said, this had nothing to do with it.

In the case of Huygens, no, they did not have big enough buffers to retransmit all of the data, but they did have a seven year flight, during which they had plenty of time to contemplate contigencies; and they did know after changing the deployment scheme there may be more ground time. Retransmitting critical data, even if it the original data was fully redundant, would have been a very cheap safety play.

Just how exactly do you propose transmitting critical data again if you don't have a big enough buffer, as you yourself admit above? The second channel WAS a contingency by itself. And it worked.

So what if Cassini wasn't even listening? And speaking of not listening, my clients and servers do an automatic cycle reset when they don't see any valid data within a specified time out period before giving up. Why was Cassini so dumb?

Do you really think giving the S/C too much autonomy at mission critical times like that is anywhere near wise? Cassini was probably in an effective safe mode during probe relay, and its only orders were to listen, record and play back. Giving it an option to automatically switch the circuits on or off might have done more harm than good.
Spacecraft designers aren't that naive -- sometimes, less is more.

Also, your client-server analogy reminds me of the sort of comparisons: my digital camera would blow away the Huygens DISR and stuff... Comparisons like that don't really do justice to anything.

Finally, if the ESA would not have revealed the loss of channel A data, would the Cassini team have taken the time to plan for such a contigency during T-13? What lessons are there to learn buried in the secret report of the DART debunkle? Let there be light.

You are trying to find connections in places where there simply aren't any. Period.