Looking at the way the system is rigged to the wall of the station is quite humorous to me in how it is taking full advantage of being weightless. From the arm the camera is attached to the tracker, and then the tracker being mounted to the one arm just seems like it would collapse on itself if it were on terra firma.
I've seen some crazy/shitty rigging done, but this one gets a pass because it's in spaaaaaaaace
I do kinda struggle to understand the geometry here though. Especially in the picture with the black-out fabric, how is the camera rotating to track stars?
In the image you referenced, the camera is tilting (or pitching, if you think in aircraft terms). Since the axis of rotation (the axle coming out of the tracker) is not super offset from the camera, the arc that the camera traces is not that wide. It seems like the surrounding blanket is mounted loosely enough to allow quite a bit of movement.
It also seems like it does not need to be capable of very long exposures, as also betrayed by the traces of the bright terrestrial lights in the demo photograph at the end.
For one of the images it says 15 second exposures. That’s a long time for something moving at orbital velocities. How is that betrayed in the image? Did you mean portrayed or displayed?
The orbital period of the ISS is 93 minutes, and it is under Earth-pointing control. That means that facing prograde (direction of travel), there will be 360° of rotation in one orbital period.
To find the angle that the camera must rotate in 15 seconds:
15sec/93min * 360° ≈ 1°
That's a lot of great information that doesn't come close to actually answering the question.
How does that image betray anything you just said. In the example image, the background is clear while the earth is a motion blur. This is obvious of a long exposure image while showing the camera is moving to track the stars with the earth is in motion below it.
If you have seen any videos from LEO satellites, including the ISS, you would notice that any particular point on the ground moves very fast from the camera's point of view.
In the photo presented on the post, you can see the tracks of man made light pollution - the bright light emanating from cities being smeared across the image plane. But you can see the start and the end of those tracks, and they are small. Which means you can gauge the relative position of a single point on the ground at the beginning and at the end of the exposure.
And it hasn't moved much. Ergo, you can estimate that the exposure time is quite small.
Let me know if that wasn't clear enough, I am not used to explaining things to this level.
So the real magic is the clock mechanism, these guys bolted a 60:90 gear pair and called it a day. How about some kudos to the engineers that made the clock and the company that made them. They can then say to their friends / family, hey one of my clocks is in space. Lots of glory to go around.
My only thought is 'RCSPAST' is the joke, but I still don't get it.
Edit: I think maybe Don's reputation as an in-space inventor (first patent for something invented in space) means the clock spring device got a long and contrived name for it's quite basic function.
I think its just them being overly technical on the naming the mechanism, ie "Rotational Coil Spring Powered", rather than just being a plain ol Windup Star Tracker
fairly easily how? bold statement with no explanation of your ideas on where the wasted mass is.
the front/back plates? looks like your standard 3/8" aluminum plates. could they have used 1/4"? other materials like plastic/carbon would probably not have passed NASA requirements. plastic/carbon could chip into small pieces which is a very bad thing on the ISS. so you're left with a metal, and aluminum is pretty safe choice. it's clear there are several holes in these plates that are not tapped and are there solely as a means to reduce the weight.
moving the pieces closer for a tighter fit resulting in a overall smaller unit size? this thing is meant for ease of use. extra space affords that, and making it more compact complicates its use.
True, I wonder how that would not be a factor, surely they always have stuff they could send up to the ISS as a backup. So if they would have made this 500g lighter, they could have sent 500g more food, for example.
I also can't imagine that the resupply flights are volume limited instead of mass.
NASA's 2-year cert for electronics requirement is puzzling. I understand rules about mission critical electronics: you want to (a) depend on it and (b) avoid fire, magic smoke, and blowing breakers on the Station. But for a non-critical application, you don't care about (a) and the risk of (b) from a 5V/2A microcontroller with a worm drive motor seems reasonably remote.
True, but even for a fully mechanical one, the one shown seems very heavy. It looks like weight wasn’t a real concern, which is strange. The plates are very thick and a lot of material could have been removed to reduce weight.
On the other hand, rocket launches produce a lot of vibration, and you don't want it to require fixing on orbit. Astronaut labor time I once saw calculated to cost something like $1M USD/astronaut/day in terms of long-tail logistical support.
Once it's up there, it's a negligible percent of the total spacecraft mass, and might be useful for later astronaut photographers.
This tripped me up:
So either this should be "... unless there was no other option", or I'm completely misunderstanding.Looking at the way the system is rigged to the wall of the station is quite humorous to me in how it is taking full advantage of being weightless. From the arm the camera is attached to the tracker, and then the tracker being mounted to the one arm just seems like it would collapse on itself if it were on terra firma.
I've seen some crazy/shitty rigging done, but this one gets a pass because it's in spaaaaaaaace
I do kinda struggle to understand the geometry here though. Especially in the picture with the black-out fabric, how is the camera rotating to track stars?
In the image you referenced, the camera is tilting (or pitching, if you think in aircraft terms). Since the axis of rotation (the axle coming out of the tracker) is not super offset from the camera, the arc that the camera traces is not that wide. It seems like the surrounding blanket is mounted loosely enough to allow quite a bit of movement.
It also seems like it does not need to be capable of very long exposures, as also betrayed by the traces of the bright terrestrial lights in the demo photograph at the end.
For one of the images it says 15 second exposures. That’s a long time for something moving at orbital velocities. How is that betrayed in the image? Did you mean portrayed or displayed?
The orbital period of the ISS is 93 minutes, and it is under Earth-pointing control. That means that facing prograde (direction of travel), there will be 360° of rotation in one orbital period.
To find the angle that the camera must rotate in 15 seconds: 15sec/93min * 360° ≈ 1°
That's a lot of great information that doesn't come close to actually answering the question.
How does that image betray anything you just said. In the example image, the background is clear while the earth is a motion blur. This is obvious of a long exposure image while showing the camera is moving to track the stars with the earth is in motion below it.
Okay, I will explain like you're 5.
If you have seen any videos from LEO satellites, including the ISS, you would notice that any particular point on the ground moves very fast from the camera's point of view.
In the photo presented on the post, you can see the tracks of man made light pollution - the bright light emanating from cities being smeared across the image plane. But you can see the start and the end of those tracks, and they are small. Which means you can gauge the relative position of a single point on the ground at the beginning and at the end of the exposure.
And it hasn't moved much. Ergo, you can estimate that the exposure time is quite small.
Let me know if that wasn't clear enough, I am not used to explaining things to this level.
So the real magic is the clock mechanism, these guys bolted a 60:90 gear pair and called it a day. How about some kudos to the engineers that made the clock and the company that made them. They can then say to their friends / family, hey one of my clocks is in space. Lots of glory to go around.
People are often quick to dismiss the impact of Starlink satellites on space photography, but here the impact is clear. Starlink ruins the photo.
> Don is a bit of a machinist himself, so we decided to have some fun with the device name.
I don’t get it, anyone able to explain?
My only thought is 'RCSPAST' is the joke, but I still don't get it.
Edit: I think maybe Don's reputation as an in-space inventor (first patent for something invented in space) means the clock spring device got a long and contrived name for it's quite basic function.
I think its just them being overly technical on the naming the mechanism, ie "Rotational Coil Spring Powered", rather than just being a plain ol Windup Star Tracker
Neat.
Debbie Downer: Looks like it fairly easily could have been made with like 50% less mass.
Perhaps that wouldn't have mattered though.
They've got the camera mounted to it using a long moment arm in one of the photos. The tracker needs to be really rigid to hold it I'd think.
"Long" = like 70 cm.
fairly easily how? bold statement with no explanation of your ideas on where the wasted mass is.
the front/back plates? looks like your standard 3/8" aluminum plates. could they have used 1/4"? other materials like plastic/carbon would probably not have passed NASA requirements. plastic/carbon could chip into small pieces which is a very bad thing on the ISS. so you're left with a metal, and aluminum is pretty safe choice. it's clear there are several holes in these plates that are not tapped and are there solely as a means to reduce the weight.
moving the pieces closer for a tighter fit resulting in a overall smaller unit size? this thing is meant for ease of use. extra space affords that, and making it more compact complicates its use.
You could have made a lot of holes on those plate to reduce weight while still having it very rigid. Those plates are extremely oversized right now.
True, I wonder how that would not be a factor, surely they always have stuff they could send up to the ISS as a backup. So if they would have made this 500g lighter, they could have sent 500g more food, for example.
I also can't imagine that the resupply flights are volume limited instead of mass.
NASA's 2-year cert for electronics requirement is puzzling. I understand rules about mission critical electronics: you want to (a) depend on it and (b) avoid fire, magic smoke, and blowing breakers on the Station. But for a non-critical application, you don't care about (a) and the risk of (b) from a 5V/2A microcontroller with a worm drive motor seems reasonably remote.
Did you mean to post this under my comment? I don’t see the connection.
Yes - it might have been 500g lighter if it wasn't fully mechanical.
True, but even for a fully mechanical one, the one shown seems very heavy. It looks like weight wasn’t a real concern, which is strange. The plates are very thick and a lot of material could have been removed to reduce weight.
On the other hand, rocket launches produce a lot of vibration, and you don't want it to require fixing on orbit. Astronaut labor time I once saw calculated to cost something like $1M USD/astronaut/day in terms of long-tail logistical support.
Once it's up there, it's a negligible percent of the total spacecraft mass, and might be useful for later astronaut photographers.
Nobody involved wants to take the risk, no matter how trivial