Kepler Telescope suffers critical failure

jj said:
Well, we did get people to/from the moon.

But, yes, I see the difficulty, it's not LEO.
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jj said:
Indeed, that is a very important point. I had though it was in LEO, but indeed I understand why it's not. If, however, it is in the earth's gravity well, a Saturn 5 setup might have been able to deal with this, except for the comment elsewhere that it is not arranged for in flight repair, which could kill the idea, except maybe for the "bolt on" arrangement.
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I'm not sure how to parse these comments of yours.

It's not in Earth orbit at all... Low, High or otherwise. It's in a Solar orbit very similar to Earth's but about 10 days longer, so it's now ~50 days or so behind us. I don't think it's in Earth's gravity well.

What is this Saturn/Large rocket rescue idea you're contemplating?
 
Thinking about momentum wheels.

Problem with wheels is that you have bearings.

It's generally not the motor that fails, but the bearings.

Things tend to weld together in vacuum, and debris does not nicely fall to the bottom of the case. Also spinning wheels can develop a charge, and this could attract the floating debris.

I think we do need to develop a fluid loop system.

Problem with a loop system is that it cannot handle anything except pointing.

It cannot kill angular momentum except by continuing to spin, which a fluid loop isn't good at.

Real reaction wheels tend to build up speed over time because of compensating for angular acceleration, and you need to use thrusters to "desaturate" the wheel.

So what you would need with a fluid loop is prompt desaturation with something like an ion attitude control thruster (like comsats use) or simply using the loop only for pointing and the thrusters for angular velocity correction.
 
Jim_MDP said:
I'm not sure how to parse these comments of yours.

It's not in Earth orbit at all... Low, High or otherwise. It's in a Solar orbit very similar to Earth's but about 10 days longer, so it's now ~50 days or so behind us. I don't think it's in Earth's gravity well.

What is this Saturn/Large rocket rescue idea you're contemplating?
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It's out of the earth's gravity well? Ok. Never mind. I did not realize it was completely out of the gravity well. Is it supposed to be headed for one of the orbital Lagrange points, then?
 
jj said:
It's out of the earth's gravity well? Ok. Never mind. I did not realize it was completely out of the gravity well. Is it supposed to be headed for one of the orbital Lagrange points, then?
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I don't know, but falling behind at only a few percent of the orbit per year, it would be a while before we lost line of sight.

As to the other part... I don't know the strength at distance of our gravity well, but earlier in the thread it was posted that the scope is ~160 times farther away than the moon.

So I was very confused by questions about "why can't we just go get it?" :D
 
Jim_MDP said:
I don't know, but falling behind at only a few percent of the orbit per year, it would be a while before we lost line of sight.

As to the other part... I don't know the strength at distance of our gravity well, but earlier in the thread it was posted that the scope is ~160 times farther away than the moon.

So I was very confused by questions about "why can't we just go get it?" :D
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I have found out that the orbit is 371 days. This is only 6 days longer than the earth. So 20 years after the launch it would be 120/365.25 * 360 = 118 degrees away from the earth. So the sun will still not be in the way of communications. Would the space craft still be producing useful data then?


http://kepler.nasa.gov/Mission/faq/#e3
 
NASA is ending recovery attempt and soliciting white papers for a two-wheeled Kepler research

Following months of analysis and testing, the Kepler Space Telescope team is ending its attempts to restore the spacecraft to full working order, and now is considering what new science research it can carry out in its current condition.

[...]

Informed by contributions from the broader science community in response to the call for scientific white papers announced Aug. 2, the Kepler project team will perform a study to identify possible science opportunities for a two-wheel Kepler mission.

Depending on the outcome of these studies, which are expected to be completed later this year, NASA will assess the scientific priority of a two-wheel Kepler mission. Such an assessment may include prioritization relative to other NASA astrophysics missions competing for operational funding at the NASA Senior Review board early next year.
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To get more information on submitting a white paper and Kepler's current capability, you can download this PDF.
 
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jj said:
Of course, since we no longer have human launch-to-orbit capacity, having fully and most likely permanently ceded military control of space to the USSR, China, and probably even the DPRK via anti-science budget cuts brought on by a bunch of YEC types who couldn't stand the evidence that was coming home, there's no way to fix this, and the USA will continue down its 2nd-world path of rot.
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Does that hobby horse ever give you saddle sores?
 
Kepler spacecraft in emergency mode

During a scheduled contact on Thursday, April 7, mission operations engineers discovered that the Kepler spacecraft was in Emergency Mode (EM). EM is the lowest operational mode and is fuel intensive. Recovering from EM is the team's priority at this time.

The mission has declared a spacecraft emergency, which provides priority access to ground-based communications at the agency's Deep Space Network.

Initial indications are that Kepler entered EM approximately 36 hours ago, before mission operations began the maneuver to orient the spacecraft to point toward the center of the Milky Way for the K2 mission's microlensing observing campaign.

The spacecraft is nearly 75 million miles from Earth, making the communication slow. Even at the speed of light, it takes 13 minutes for a signal to travel to the spacecraft and back.

The last regular contact with the spacecraft was on April. 4. The spacecraft was in good health and operating as expected.

Kepler completed its prime mission in 2012, detecting nearly 5,000 exoplanets, of which, more than 1,000 have been confirmed. In 2014 the Kepler spacecraft began a new mission called K2. In this extended mission, K2 continues the search for exoplanets while introducing new research opportunities to study young stars, supernovae, and many other astronomical objects.

Updates will be provided as additional information is available.
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Kepler Recovered from Emergency and Stable

Mission operations engineers have successfully recovered the Kepler spacecraft from Emergency Mode (EM). On Sunday morning, the spacecraft reached a stable state with the communication antenna pointed toward Earth, enabling telemetry and historical event data to be downloaded to the ground. The spacecraft is operating in its lowest fuel-burn mode
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https://www.nasa.gov/feature/mission-manager-update-kepler-recovered-from-emergency-and-stable
 
Puppycow said:
Can it return to its primary mission, or is its attitude control not good enough for that?
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Primary mission ended when it lost 2 of 4 reaction wheels. The current mission is named "K2" and incorporates an optical sensor of some kind (article I read didn't go into details) to track our sun for a third point of reference. It isn't as accurate as the original mission but is still finding exoplanets.
 
Ball Aerospace star trackers are 3rd or 4th generation and provide an attitude reference. It is the reaction wheels that provide attitude control. You need only three, but four are provided for redundancy. They are arranged in non-orthogonal orientations such that any required control moment can be expressed as a vector sum of any 3 reaction wheels. However, with two non-functioning reaction wheels you can apply only a subset of needed control moments. The limp mode being used here incorporates solar wind pressure. Normally that would be a perturbing effect.
 
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