It seems like an absolute encoder would immediately lose its advantages if a reduction gear were used though? Then you would still need to rehome the number of revolutions.
You can get multi-turn absolute encoders for these applications.
Readit Newsonetwentythree commented on Servo vs. steppers: Speed, Torque and Accuracy [video] youtube.com/watch?v=H-nO1... · Posted by u/f1shy
This is that odd space law case where the Chinese just let their rockets reenter wherever, and it’s just debris, but SpaceX tries to deorbit in a specific spot, and are in trouble if they miss. What a perverse incentive.
I don’t think they’re in trouble for missing the deorbit target.
The concern is that the second stage didn’t perform as expected. What if that affects the primary mission on the next flight? They need to understand the root cause before they fly again.
As the article states, the upcoming Europa Clipper launch requires an upper stage relight to put the spacecraft on the desired trajectory. If the second burn does not go as expected, the mission could be in jeopardy.
onetwentythree commented on Linksys WRT54G and WRT54GS power supply (2005) kioan.users.uth.gr/wirele... · Posted by u/peter_d_sherman
The problem is the voltage drop. The bigger voltage difference it has to handle, the hotter it gets as its the loss from "internal loss current x voltage drop" is converted into hat.
That only applies to linear regulators.
The router on this page uses a switching regulator. Switching regulators have a relatively constant power draw over the entire input voltage range.
Do any probes publish protocols that have distinct receive or telemetry protocols? Would be cool to be able to listen in to some of the closer ones, if possible.
Not sure about a mission as old as voyager, but most modern missions use CCSDS protocols, which are open and available online.
But just because you know the protocol dues not mean you have enough information to send a valid command. The commands are wrapped in a common protocol, but the commands themselves are typically mission-specific and definitely not made public.
Here’s an example of someone unaffiliated with the mission decoding JWST telemetry. While they were able to identify the packets defined per CCSDS protocols, they do not know the actual content of the packets, which are mission specific.
https://destevez.net/2021/12/decoding-james-webb-space-teles...
And as someone else mentioned, the biggest hurdle with getting a command to voyager is access to a 70 m dish. Not many of those floating around…
onetwentythree commented on Juice’s RIME antenna successfully unjammed esa.int/Science_Explorati... · Posted by u/zdw
I don't think a shape memory alloy would provide a shock. I suspect they are solenoids(vs explosive bolts) used to detach the vehicle from it's mounting plate on the rocket. and the engineers as they went down the list trying increasingly wild ideas to get the antenna to deploy reached "fire the release solenoids, and hope it shakes the antenna pin in the correct way".
It did, so slow clap for the engineers for saving a very expensive science experiment remotely from billions of miles away. well done.
The shock typically comes from the release of the preload, not from the NEA itself.
"There’s going to be a boarding party on the first of October next year,” says Alan Stern, the mission’s principal investigator"
I think the unstated is that the original group of scientists feels like they are being put out to pasture in favor of a new set of researchers. But as you mentioned, if there aren't any more Kuiper belt objects on the "horizon", it seems like the right move.
Maybe I’m wrong, but having it classified as a planetary mission probably funds their positions and a lot of continued research (even if the research is based on data already taken). Reclassifying the mission probably means the scientists need to look for new sources of funding. So I get that they’re not happy, but it sounds like a rational decision on NASA’s part.
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onetwentythree commented on The Webb Space Telescope’s profound data challenges spectrum.ieee.org/james-w... · Posted by u/MindGods
Oh, the antenna doesn't need to just point in the general direction of Earth, it needs to point to somewhere in the surface. That makes sense, having a narrower beam would save power and achieve higher bitrates
Does this mean it has only a 12-hour window to transmit? Or there's multiple antennas on Earth?
It uses NASA’s Deep Space Network. There are three stations around the globe (California, Australia, and Spain), spaced so that there is near continuous coverage for deep space missions. JWST points it’s antenna at the station that is currently in view.
However, the ground stations are shared between many missions, so they are not available for JWST all the time. Expectation is that JWST gets 8-12 hours/day of DSN time.
onetwentythree commented on The Webb Space Telescope’s profound data challenges spectrum.ieee.org/james-w... · Posted by u/MindGods
> Data gathered from its scientific instruments, once collected, is stored within the spacecraft’s 68-GB solid-state drive (3 percent is reserved for engineering and telemetry data)
Hope the SSD does not fail after 32768 or 40000 hours of operation.
I know this is a joke but...
JWST does not use a typical flash-based SSD. The mass storage is all SDRAM. There are layers of error correction and scrubbing to handle bit flips.
onetwentythree commented on The Webb Space Telescope’s profound data challenges spectrum.ieee.org/james-w... · Posted by u/MindGods
> JWST is transmitting data back to Earth on a 25.9-gigahertz channel at up to 28 megabits per secon
0.028*3600 = 100 Gbit/hour
No problem here.
There are only 8 hours of downlink time per day. DSN resources are limited and shared among many missions.
Everything was sized based on the expected volume of data that the telescope would be able to take. The instruments only generatedata at a certain rate, and there are inefficiencies involved with slewing between targets. Having a larger recorder or faster downlink would not mean that JWST could take more science data.