Two of four reaction wheels seized up, critical for precise photometry
Excerpt from the Kepler Mission Manager Update. (h/t to Dr. Leif Svalgaard)
At our semi-weekly contact on Tuesday, May 14, 2013, we found the Kepler spacecraft once again in safe mode. As was the case earlier this month, this was a Thruster-Controlled Safe Mode. The root cause is not yet known, however the proximate cause appears to be an attitude error….
…We attempted to return to reaction wheel control as the spacecraft rotated into communication…but reaction wheel 4 remained at full torque while the spin rate dropped to zero. This is a clear indication that there has been an internal failure within the reaction wheel, likely a structural failure of the wheel bearing. The spacecraft was then transitioned back to Thruster-Controlled Safe Mode.
An Anomaly Review Board concurred that the data appear to unambiguously indicate a wheel 4 failure, and that the team’s priority is to complete preparations to enter Point Rest State. Point Rest State is a loosely-pointed, thruster-controlled state that minimizes fuels usage while providing a continuous X-band communication downlink. The software to execute that state was loaded to the spacecraft last week, and last night the team completed the upload of the parameters the software will use.
The spacecraft is stable and safe, if still burning fuel…In its current mode, our fuel will last for several months. Point Rest State would extend that period to years.
…We will take the next several days and weeks to assess our options and develop new command products. These options are likely to include steps to attempt to recover wheel functionality and to investigate the utility of a hybrid mode, using both wheels and thrusters.
With the failure of a second reaction wheel, it’s unlikely that the spacecraft will be able to return to the high pointing accuracy that enables its high-precision photometry. However, no decision has been made to end data collection.
Kepler had successfully completed its primary three-and-a-half year mission and entered an extended mission phase in November 2012.
Even if data collection were to end, the mission has substantial quantities of data on the ground yet to be fully analyzed, and the string of scientific discoveries is expected to continue for years to come….
Read the full Mission Manager Update.
In a New York Times article, astronaut John Grunsfeld, now in charge of NASA Science Mission Directorate under which Kepler operates, is quoted: “For Mr. Grunsfeld, who played mechanic to the Hubble telescope during several lengthy spacewalks, the Kepler malfunction looked particularly frustrating. ‘Unfortunately, it’s not in a place where I can go and fix it,’ he said.”
What does reaction wheel 4 look like?
(see photo at right)
Where are the reaction wheels on the spacecraft?
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Wow, Wamron — thanks for the EXCELLENT cameras (and more — neat photo contest winners on “Earth and Sky” — beautiful (most)) site. I was just now reading and researching and realized, “Hey, I’d better acknowledge W’s kindness before ANOTHER half an hour goes by!”
Lol Wamron… some people like holding a giant camera up to poke their eyes into… I don’t. To me the digital back is better because it shows what the image will look like, not what I wish it would look like.
Everyone’s preference varies.. to each their own.
Code Tech.., An eye-level viewfinder can be optical OR electronic. All bridge cameras and now many interchangeable lense system cameras have an EVF which shows exactly the same image as the monitor. Many SLRS now have a live view monitor as well as all Sony SLT cameras. You can use either viewfinder or monitor depending on the situation. But the eye level finder usually wins because it permits you to brace the camera against your head with elbows in and body stable.This creates great stability especially useful with long focal lengths or at night. It also permits you to eye-explore the entire frame to the edges without the least wandering between composition and shutter release. If you want low or high angle shots you then switch over to the monitor. You can if you wish buy an external EVF to fit onto your Sony.
This is partly why I prefer my Sony R1 with EVF to the Sony SLRs I have, apart from its phenomenal lens quality. You DO see exactly what the sensor sees, but in an eye-level finder.
The use of a monitor, on the other hand, echoes the waist-level viewfinders on medium format film cameras. But even then, when not using a tripod it is customary to use a flip out magnifier and place the hood against the eye. As with my Mamiya system cameras. Funny enough, such magnifier hoods are actually made to use on digital cameras that rely on a monitor! Another example of plus ca change.
Then of course, the R1 is designed with the monitor on top to resemble the very same arrangement as on a Hasselblador my Mamiya 645 so the feel of the camera echoes medium format. and I do use that monitor with a magnifier hood, as you would with a Mamiya, a Bronica or a Hasselblad.
Janice…one last point from me on this thread, did you notice they have an item in the news column at that site that mentions Dageurrotypes?
Now I must go and be grumpy somewhere.
Yes, Grumpy #[;)], I did. I was going to mention that to you and forgot. I clicked on it, but, didn’t keep on clicking to get to the actual video — bailed out to go look at cameras. I’ll be returning to that site again and again, I’m sure.
Thanks so much for all your help. Happy shooting!
Soon, I will be Sleepy. 🙂 Not likely to ever be Bashful, though, heh, heh.
(YES, AndyG, I LIKE “Snow White and the Seven Dwarfs — stupid in parts, but, overall, wonderful)
As I said, to each their own. I hate using a viewfinder, and I hate holding a giant camera in front of my face. Some people prefer it. To each their own. The NEX screen folds out and points up or down so you can hold it high or low. To me, for the style of shooting I do, it’s a better way to frame pictures. Of course, what do I know, I’m only currently making a living shooting pictures.
My girlfriend prefers holding the camera in front of her face. It hides her while she’s shooting. She’s starting to realize the NEX is getting better shots since we sometimes go on shoots together.
I would never tell someone blocking their face with a big camera that they’re “doing it wrong”, because I used to use 35mm cameras too. If I need more stability I use a tripod or monopod.