Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
albertson.ch...@gmail.com said: What stops working when things get cold? On Mars, the solar cells are pointed in the right direction. Why doesn't it recover when the sun comes back in the Spring? They run out of power for running the battery heaters, then the battery freezes and fails. The batteries get to such a low temperature that they are unable to be charged. The rover was never designed so that it could move and operate under solar power. It is really battery powered and uses the panel for charging. We are talking about running computers and radio gear rather than motors. I can see running motors in bursts from batteries, but computers and radios generally run continuously so they shouldn't need a battery when the sun is up. Am I missing something? Can't the computers and radios run off solar power when the batteries are dead? Does the receiver take more than (ballpark) peak solar-cell output under nasty conditions? jim...@earthlink.net said: That 10-20 degrees makes a big difference because of the cosine (angle) problem/ I understand that it could make the critical difference, but COS 20 is still close to 1. It's probably lost in the noise of how much dirt is on the solar cells. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
There is a major problem with Radioisotope Thermoelectric Generators Our stocks of Plutonium-238 are very low -- less than 40 pounds remain available to NASA and this is all spoken for future missions. We are restarting the manufacture and it is supposed to come online sometime around 2017. One gram of Plutonium-238 gives about 0.5 watts of deliverable electricity. Half-life of 87.7 years. P-238 does not go KaBoom! -- you are thinking of P-239. http://en.wikipedia.org/wiki/Plutonium-238 http://www.space.com/20290-plutonium-spacecraft-nasa-fuel.html http://www.wired.com/wiredscience/2013/09/plutonium-238-history-timeline/ -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson Sent: Saturday, September 21, 2013 20:34 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem On Sat, Sep 21, 2013 at 6:40 PM, Hal Murray hmur...@megapathdsl.net wrote: What stops working when things get cold? On Mars, the solar cells are pointed in the right direction. Why doesn't it recover when the sun comes back in the Spring? They run out of power for running the battery heaters, then the battery freezes and fails. The batteries get to such a low temperature that they are unable to be charged. The rover was never designed so that it could move and operate under solar power. It is really battery powered and uses the panel for charging. This is the biggest reason the newest rover, Curiosity is powered by an RTG, not solar cells. The RTG is powered by radioactive decay. The thing makes a lot of heat and should last 15 to 20 years. Likely longer than all the moving parts like motors and so on. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
On 9/21/13 11:03 PM, Hal Murray wrote: albertson.ch...@gmail.com said: What stops working when things get cold? On Mars, the solar cells are pointed in the right direction. Why doesn't it recover when the sun comes back in the Spring? They run out of power for running the battery heaters, then the battery freezes and fails. The batteries get to such a low temperature that they are unable to be charged. The rover was never designed so that it could move and operate under solar power. It is really battery powered and uses the panel for charging. We are talking about running computers and radio gear rather than motors. I can see running motors in bursts from batteries, but computers and radios generally run continuously so they shouldn't need a battery when the sun is up. The computers and radios and instruments actually take more power than the motors. MER doesn't have very big motors. It only moves a few cm/sec. For instance, to fire up the radio to talk to earth, either via the relay link or direct on X-band, is probably around 50 watts. MER has maybe 1 square meter of solar panels, it's farther from the sun, etc. It probably has positive energy balance when the sun is shining in the summer and running the flight computer and radios. The problem is running the heaters in the cold. In the winter, it gets colder AND there's less solar energy from the panels. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
Well, since this thread has recurred and there seem to be people with good knowledge here, I've got to ask how a spacecraft that has lost its ability to aim antennas at Earth or align solar panels with the sun could possibly be diagnosed with having a time tagging problem? Jim Lux pretty well demolished the idea that time had anything to do with it, IMHO. Seems to me that the DSN doesn't listen to Deep Impact continuously because it has other spacecraft to track. So there's no growing anomaly to indicate a future problem. One time communication is fine, the next time there is no answer. Pretty difficult to diagnose a problem from those symptoms. Used silver cell batteries for an upper atmosphere density probe in 1958. They're still around, but not suitable for long missions. What kind of battery (not RTG) would a deep space probe use? Thanks for any answers. Bill Hawkins ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
On 9/22/13 10:07 AM, Bill Hawkins wrote: Well, since this thread has recurred and there seem to be people with good knowledge here, I've got to ask how a spacecraft that has lost its ability to aim antennas at Earth or align solar panels with the sun could possibly be diagnosed with having a time tagging problem? Most likely because the telemetry (which is time tagged in several ways) didn't make sense. If you got frames down and the spacecraft time wasn't monotonically increasing, you're pretty sure you've had a reset. For that matter, there's a sequence number in the transfer frames, and if that reset, you'd see it. I don't know what the format of the DI telemetry frame is (it's probably published.. in general, telemetry isn't export controlled) but a typical scheme has the SCLK (spacecraft clock) in every frame, or every N frames. The question is whether they have all the bits of sclk all the time, or just the LSBs all the time, and the MSBs occasionally. DI is a fairly old design, so the telemetry format probably isn't very complex (e.g. it's not like they have dynamically allocated data fields, etc.) Jim Lux pretty well demolished the idea that time had anything to do with it, IMHO. Seems to me that the DSN doesn't listen to Deep Impact continuously because it has other spacecraft to track. Yes. There's probably 50 spacecraft that DSN is tracking. As I recall, they track Voyager once a week or maybe every other week. There's actually a published schedule on a regularly updated website. So there's no growing anomaly to indicate a future problem. One time communication is fine, the next time there is no answer. Pretty difficult to diagnose a problem from those symptoms. Well.. if the s/c is in safe mode, it's sending data at something like 10bps or 7-8 bps. And that data will have a sequence number or clock time in it, and you might be able to infer what's going on from that. Or, they have a trickle back scheme that sends a few words of memory in every frame, so that after enough frames, you have an image of memory. Used silver cell batteries for an upper atmosphere density probe in 1958. They're still around, but not suitable for long missions. What kind of battery (not RTG) would a deep space probe use? for rechargeable? NiCd (in the past) Lithium Ion (now) A lot also depends on temperature range expected. Most orbiters even around Mars, stay nice and toasty warm without much work, as long as the thermal design was decent. A shiny metal ball in orbit around Mars will get quite warm. I don't know if it would get to 60-78C, but it definitely will get to 30C. It's all about alpha/epsilon ratios. But different battery chemistry has different temperature range tolerances. And then, there's the whole will it have charge after it thaws question. I have some supercaps that I've been meaning to freeze to try it out (or at least to see if they'll survive) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Space mission comes to an end becuase of a computer time tagging problem
And my favorites: Nickel-Hyrdogen cells and their silvery cousins. You have to work REALLY hard to kill them. --- for rechargeable? NiCd (in the past) Lithium Ion (now) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
On Sat, Sep 21, 2013 at 11:03 PM, Hal Murray hmur...@megapathdsl.net wrote: We are talking about running computers and radio gear rather than motors. I can see running motors in bursts from batteries, but computers and radios generally run continuously so they shouldn't need a battery when the sun is up. Am I missing something? Can't the computers and radios run off solar power when the batteries are dead? Does the receiver take more than (ballpark) peak solar-cell output under nasty conditions? I jst looked up some specs. The electronic is housed in a heated box. Apparently if the heat goes away some parts fail. Also it is a close call if the radio and computer could run under solar power alone. It can if the communications path uses a Mars orbiting relay but it takes 55W to transmit directly to Earth and the computer burns 15W. The computer can't run full time. It uses to much power so the solar charger has a built-in timer that can wake the computer. I looks like normal operation is to let the battery charge while the computer and everything thing else of powered down, then after so much time the charger wakes the computer so it can do something, then back to charging.This lets them do work with very degraded solar cells.But at some point the battery freeze and the heated electronics box can't be kept warm any more.This was a reasonable design for a system that had a 90 day planned operational lifetime. There are a lot of things they could have done. For example why not push the arm into the ground hard enough to left the front wheels and tilt the panels square to the sun? I guess the added weight of the more robust arm was not worth it. They had a weight, volume and cost and time budget to work with. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
On 9/22/13 4:48 PM, Mark Sims wrote: And my favorites: Nickel-Hyrdogen cells and their silvery cousins. You have to work REALLY hard to kill them. Yes, forgot the NiMH too.. although they self discharge --- for rechargeable? NiCd (in the past) Lithium Ion (now) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Space mission comes to an end becuase of a computer time tagging problem
No, I'm talking about nickel/gaseous hydrogen cells. Basically they can't be overcharged/overdischarged/frozen to death. State of charge can be determined by a pressure reading. Can be cycled a zillion times. -- And my favorites: Nickel-Hyrdogen cells and their silvery cousins. You have to work REALLY hard to kill them. Yes, forgot the NiMH too.. although they self discharge ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
On 9/20/13 5:12 PM, Bob Camp wrote: Hi Low bid wrist watch used as time base? - I'd bet there is some form of master time tick in their RTOS that keeps everything pumping. Loose the time tick (or the time tick count) and it all goes away… yes and no. Most spacecraft have a default strategy if everything got reset, so they don't need to know what time it is. They go into safe hold mode. There's several steps in the strategy. If you have attitude knowledge, you'll sun/earth point the high gain antenna and wait to hear from the ground. If you don't have attitude knowledge, you shift to the low gain omni antenna, and wait to hear from the ground. DSN cranks up the Tx power, and they transmit at a very low rate (10 bits/sec) to try and get a command in through the LGA. If you've totally lost attitude control, and you're slowly rotating, you still might not get a command it, because there's no such thing as a truly omni antenna pattern: it has lumps and bumps and nulls. However, unless there's no attitude control authority (e.g. if you have wheels and they've failed, or you've run out of propellant), you don't need to know the time to be able to stabilize the spacecraft in one attitude. And once you're stabilized, you can get that command in. So there's some other more complex problem. As the onboard computers accumulate radiation induced faults, there's a lot of software patching that goes on to map around the faulty sections. They may have done one to may patches. I don't think that is the case with DI. Radiation causes upsets, but they're usually a transient thing, and rewriting the memory fixes it. Most of the time it's using EDAC on the memory, and scrubbing. One can send commands from the ground that will kill it accidentally. Spacecraft have typically very simple command structures. A lot of commands are basically poke this value at this address and with knowledge on the ground of which control paramters are stored at which addresses, you can build your commands. However, if you poke the wrong address, or send the wrong value, you can command the spacecraft to do something that is irrecoverable. One of the Mars spacecraft was lost because of this. People often ask why doesn't it have range checking and validation on the parameters. Well.. that would take more code, and memory is a limited resource. And, it's not like there's a command parser in the sense of a shell that interprets and validates commands. The spacecraft checks the checksum on the received message, and does it. This comes from a long history where spacecraft had very simple control systems (no computer). You'd have a bunch of relays and the message that comes up has a bit for each relay or control line. The command detector unit sees the frame sync bit sequence and then just loads the bits into a big register, and when the checksum is ok, it latches them all in. It's much like how 1553 works. You assign each word or bit to some actuator or sensor, and it's more like remote memory access than actual commanding. The whole process works the same on downlink. In fact, even though we now use computers, it's still called decommutation Bob ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
from JPL http://www.jpl.nasa.gov/news/news.php?release=2013-275 Mission controllers postulate that there was an anomaly generated by the spacecraft's software which left the vehicle's computers in a condition where they are continuously rebooting themselves. If this is the case, the computers would not continue to command the vehicle's thrusters to fire and hold attitude. Lack of attitude hold makes attempts to reestablish communications more difficult because the orientation of the spacecraft's antennas is unknown. It also brings into question the vehicle's electrical power status, as the spacecraft derives its power from a solar array that is fixed, with its cells pointing in one direction. If it gets cold enough (without power from solar cells, it won't generate enough internal heat to keep warm), it will die. That's probably what happened to Spirit on Mars. It got cold enough during the Martian winter, and with not enough solar power, enough things drifted cold enough that we couldn't get commands in. BTW, DI uses star trackers for attitude knowledge, so it has the potential to point very precisely. If anyone is interested in the gory details of how the telecom system works http://descanso.jpl.nasa.gov/DPSummary/di_article_cmp20050922.pdf Page 20 shows the variation in AuxOsc frequency of the SDST radio vs temperature. That shape will look pretty familiar to list members. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
Hi So it's a pretty good AT cut crystal without any compensation of heating. Not quite a cheap wrist watch, but not a BVA in a dewar flask either. Bob On Sep 21, 2013, at 8:11 AM, Jim Lux jim...@earthlink.net wrote: from JPL http://www.jpl.nasa.gov/news/news.php?release=2013-275 Mission controllers postulate that there was an anomaly generated by the spacecraft's software which left the vehicle's computers in a condition where they are continuously rebooting themselves. If this is the case, the computers would not continue to command the vehicle's thrusters to fire and hold attitude. Lack of attitude hold makes attempts to reestablish communications more difficult because the orientation of the spacecraft's antennas is unknown. It also brings into question the vehicle's electrical power status, as the spacecraft derives its power from a solar array that is fixed, with its cells pointing in one direction. If it gets cold enough (without power from solar cells, it won't generate enough internal heat to keep warm), it will die. That's probably what happened to Spirit on Mars. It got cold enough during the Martian winter, and with not enough solar power, enough things drifted cold enough that we couldn't get commands in. BTW, DI uses star trackers for attitude knowledge, so it has the potential to point very precisely. If anyone is interested in the gory details of how the telecom system works http://descanso.jpl.nasa.gov/DPSummary/di_article_cmp20050922.pdf Page 20 shows the variation in AuxOsc frequency of the SDST radio vs temperature. That shape will look pretty familiar to list members. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
On 09/21/2013 02:52 PM, Bob Camp wrote: Hi So it's a pretty good AT cut crystal without any compensation of heating. Not quite a cheap wrist watch, but not a BVA in a dewar flask either. The environmental perturbations should go quite slow most of the time, as it glides in the void slowly away and often have a fairly stable direction with regards to the sun. If they have spin-rotation it complicates things a bit. Decent dewar-flask with better background radiation and one major heat source that you track for the solar panels. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
On 9/21/13 5:52 AM, Bob Camp wrote: Hi So it's a pretty good AT cut crystal without any compensation of heating. Not quite a cheap wrist watch, but not a BVA in a dewar flask either. Yep. The AuxOsc is what is used if you don't want to have the downlink locked to the uplink. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
On 9/21/13 6:03 AM, Magnus Danielson wrote: On 09/21/2013 02:52 PM, Bob Camp wrote: Hi So it's a pretty good AT cut crystal without any compensation of heating. Not quite a cheap wrist watch, but not a BVA in a dewar flask either. The environmental perturbations should go quite slow most of the time, as it glides in the void slowly away and often have a fairly stable direction with regards to the sun. If they have spin-rotation it complicates things a bit. Decent dewar-flask with better background radiation and one major heat source that you track for the solar panels. Yeah, there's jokes about why are they obsessing about hermetic seals on components when we're going to be operating in a harder vacuum than you can easily achieve on earth. The outside of the package probably has a lower pressure than inside the package. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
On 09/21/2013 03:26 PM, Jim Lux wrote: On 9/21/13 6:03 AM, Magnus Danielson wrote: On 09/21/2013 02:52 PM, Bob Camp wrote: Hi So it's a pretty good AT cut crystal without any compensation of heating. Not quite a cheap wrist watch, but not a BVA in a dewar flask either. The environmental perturbations should go quite slow most of the time, as it glides in the void slowly away and often have a fairly stable direction with regards to the sun. If they have spin-rotation it complicates things a bit. Decent dewar-flask with better background radiation and one major heat source that you track for the solar panels. Yeah, there's jokes about why are they obsessing about hermetic seals on components when we're going to be operating in a harder vacuum than you can easily achieve on earth. The outside of the package probably has a lower pressure than inside the package. True. The trouble is really what happens prior to reaching that hard vacuum. You could do a in space pumping by having the thing pressurized and then heat up a lead-plug until it melts and the pressure shoots out the blob, gas and eventually the innards decays into hard vacuum. If you do that early in the mission, the handling the shift is relatively easy as C/N ratios is favorable. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
from JPL http://www.jpl.nasa.gov/news/news.php?release=2013-275 Mission controllers postulate that there was an anomaly generated by the spacecraft's software which left the vehicle's computers in a condition where they are continuously rebooting themselves. If this is the case, the computers would not continue to command the vehicle's thrusters to fire and hold attitude. Lack of attitude hold makes attempts to reestablish communications more difficult because the orientation of the spacecraft's antennas is unknown. It also brings into question the vehicle's electrical power status, as the spacecraft derives its power from a solar array that is fixed, with its cells pointing in one direction. If it gets cold enough (without power from solar cells, it won't generate enough internal heat to keep warm), it will die. That's probably what happened to Spirit on Mars. It got cold enough during the Martian winter, and with not enough solar power, enough things drifted cold enough that we couldn't get commands in. BTW, DI uses star trackers for attitude knowledge, so it has the potential to point very precisely. If anyone is interested in the gory details of how the telecom system works http://descanso.jpl.nasa.gov/DPSummary/di_article_cmp20050922.pdf Page 20 shows the variation in AuxOsc frequency of the SDST radio vs temperature. That shape will look pretty familiar to list members. ___ Thanks, Jim, for the press release details, and the article pointer. Still doesn't say what the anomaly was, but I guess we will never know. Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
jim...@earthlink.net said: If it gets cold enough (without power from solar cells, it won't generate enough internal heat to keep warm), it will die. That's probably what happened to Spirit on Mars. It got cold enough during the Martian winter, and with not enough solar power, enough things drifted cold enough that we couldn't get commands in. What stops working when things get cold? On Mars, the solar cells are pointed in the right direction. Why doesn't it recover when the sun comes back in the Spring? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
On 9/21/13 6:40 PM, Hal Murray wrote: jim...@earthlink.net said: If it gets cold enough (without power from solar cells, it won't generate enough internal heat to keep warm), it will die. That's probably what happened to Spirit on Mars. It got cold enough during the Martian winter, and with not enough solar power, enough things drifted cold enough that we couldn't get commands in. What stops working when things get cold? Lots of things. Mars gets *really cold* in the winter (-50C and lower) There's an issue with plastic packages where it gets brittle. CTE mismatches cause cracks, etc. Electrolytic capacitors freeze. On Mars, the solar cells are pointed in the right direction. Why doesn't it recover when the sun comes back in the Spring? for Spirit, because of the issues with the wheel drive motors, it couldn't get into the right position to face the sun (on a south facing hillside, basically) That 10-20 degrees makes a big difference because of the cosine (angle) problem/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
On Sat, Sep 21, 2013 at 6:40 PM, Hal Murray hmur...@megapathdsl.net wrote: What stops working when things get cold? On Mars, the solar cells are pointed in the right direction. Why doesn't it recover when the sun comes back in the Spring? They run out of power for running the battery heaters, then the battery freezes and fails. The batteries get to such a low temperature that they are unable to be charged. The rover was never designed so that it could move and operate under solar power. It is really battery powered and uses the panel for charging. This is the biggest reason the newest rover, Curiosity is powered by an RTG, not solar cells. The RTG is powered by radioactive decay. The thing makes a lot of heat and should last 15 to 20 years. Likely longer than all the moving parts like motors and so on. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Space mission comes to an end becuase of a computer time tagging problem
NASA's Deep Space Comet Hunter Mission Comes to an end The news release includes this paragraph: After losing contact with the spacecraft last month, mission controllers spent several weeks trying to uplink commands to reactivate its onboard systems. Although the exact cause of the loss is not known, analysis has uncovered a potential problem with computer time tagging that could have led to loss of control for Deep Impact's orientation. That would then affect the positioning of its radio antennas, making communication difficult, as well as its solar arrays, which would in turn prevent the spacecraft from getting power and allow cold temperatures to ruin onboard equipment, essentially freezing its battery and propulsion systems. Knowing the membership of this group, does anyone have more insight into what the computer time tagging problem might be? Thanks, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
Winders? -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David J Taylor Sent: Saturday, 21 September 2013 2:51 AM To: Time-nuts mailing list Subject: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem NASA's Deep Space Comet Hunter Mission Comes to an end The news release includes this paragraph: After losing contact with the spacecraft last month, mission controllers spent several weeks trying to uplink commands to reactivate its onboard systems. Although the exact cause of the loss is not known, analysis has uncovered a potential problem with computer time tagging that could have led to loss of control for Deep Impact's orientation. That would then affect the positioning of its radio antennas, making communication difficult, as well as its solar arrays, which would in turn prevent the spacecraft from getting power and allow cold temperatures to ruin onboard equipment, essentially freezing its battery and propulsion systems. Knowing the membership of this group, does anyone have more insight into what the computer time tagging problem might be? Thanks, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem
Hi Low bid wrist watch used as time base? - I'd bet there is some form of master time tick in their RTOS that keeps everything pumping. Loose the time tick (or the time tick count) and it all goes away… As the onboard computers accumulate radiation induced faults, there's a lot of software patching that goes on to map around the faulty sections. They may have done one to may patches. Bob On Sep 20, 2013, at 7:47 PM, Mark C. Stephens ma...@non-stop.com.au wrote: Winders? -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David J Taylor Sent: Saturday, 21 September 2013 2:51 AM To: Time-nuts mailing list Subject: [time-nuts] Space mission comes to an end becuase of a computer time tagging problem NASA's Deep Space Comet Hunter Mission Comes to an end The news release includes this paragraph: After losing contact with the spacecraft last month, mission controllers spent several weeks trying to uplink commands to reactivate its onboard systems. Although the exact cause of the loss is not known, analysis has uncovered a potential problem with computer time tagging that could have led to loss of control for Deep Impact's orientation. That would then affect the positioning of its radio antennas, making communication difficult, as well as its solar arrays, which would in turn prevent the spacecraft from getting power and allow cold temperatures to ruin onboard equipment, essentially freezing its battery and propulsion systems. Knowing the membership of this group, does anyone have more insight into what the computer time tagging problem might be? Thanks, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
