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NASA Abandons Kepler Repairs, Looks To the Future
cylonlover writes "If NASA has anything to say about it, Kepler is down, but not out. At a press teleconference on Thursday it announced that it has abandoned efforts to repair the damaged unmanned probe, which was designed to search for extrasolar planets and is no longer steady enough to continue its hunt. But the space agency is looking into alternative missions for the spacecraft based on its remaining capabilities. 'On Aug. 8, engineers conducted a system-level performance test to evaluate Kepler's current capabilities. They determined wheel 2, which failed last year, can no longer provide the precision pointing necessary for science data collection. The spacecraft was returned to its point rest state, which is a stable configuration where Kepler uses thrusters to control its pointing with minimal fuel use.'"
as with most satellite missions gone wrong -- its was the gyroscope.... remember it was replaced on Hubble a few times... its seems to be the weakest link in a lot of missions as it has to be a moving part to induce counter rotation in the satellite. it's only feasible to put so many on board ... so maybe a redesign of this one part will save future missions ... but maybe its time to think outside the box now that we know ion drives work a kg of propellant and three exhuast ports would fix this issue with new tech
Other than that it was an awesome mission.
It seems that NASA is challenging the scientific community to come up with new projects or experiments that could still work despite the Kepler's limitations now. So it is time for all the scientists with their eyes toward the sky to start dusting off the keyboards and to come up with some cool new proposals. So even though it was not a screaming success the project could still turn out to be important to the scientific community going forward. If we have some scientists who can come up with neat ideas on how to use the capabilities this device still has.
ACK
as with most satellite missions gone wrong -- its was the gyroscope
Actually the gyroscopes lasted the original 3.5 year mission, but due to more noise than anticipated they collected less data than planned - which was why the mission was extended to 7.5 years. Now they won't be able to finish that, but that was really the backup plan failing. Oh well, not everything can be a Mars Rover exceeding all design specs by leaps and bounds.
Live today, because you never know what tomorrow brings
deploy another gyroscope and rpg in a package that can be attached to Kepler, a practice run for comet sampling missions
To nitpick, they collected as much data as planned, but it was noisier than expected. Therefore they needed more data to bring the signal above the noise. Interestingly the source of the noise isn't Kepler, but sunspots on the stars causing fluctuations in the brightness. They'd counted on a 3.5 year mission being long enough to collect a strong enough signal by assuming sunspot noise was the same as from the Sun, but it turned out it was actually stronger.
No kidding!!! What do you say at this point?
You can control attitude using (ion) thruster, but reaction wheels have some advantages. One of the biggest advantage of RWs is that it's (close to) a linear actuator (outside of the zero crossing zone), where thruster are bang bang actuators. In fact they are bad bang bang actuator, because you have some transient at start and end of the pulse.
Didn't NASA have reaction wheels go on another probe as well? The one we're sending to explore Ceres I think had reaction wheel issues as well and had to be reconfigured to run its mission on thrusters as well.
Reaction wheels a very well known concepts in spaceflight. The ISS uses them to point itself (The Control Moment Gyros) and pretty much any and all geosynchronous satellites also use reaction wheels to keep themselves pointed at earth. This is actually how they ended up recovering Galaxy 15. After several months of drifting while "zombie", the reaction wheels finally saturated (spinning as fast as they could go) causing the satellite to lose earth lock, and go into a safe mode.
Anyhow, the upside and downside is that they are relatively simple devices, and allow for very precise and stable pointing without spending a lot of fuel (you don't want your exhaust condensing on your optics in a telescope now do you?), but at the same time they're mechanical devices, and thus are more fragile than something that's purely solid state.
...si hoc legere nimium eruditionis habes...
Given how common this mode of failure is, throwing a lot of money into the study of better reaction wheel designs would probably pay off for a slew of future missions.
[I can't believe I just said that]
The problem is Kepler doesn't really have the resolution for things we're interested in and may not actually be able to be pointed in certain directions due to solar panel and communications relay positioning. Best we could come up with at our brainstorming meeting this morning was parallax with our upcoming mission to Pluto and to resolve a bet on whether or not ISON will explode when it passes close to the sun later this year.