SpaceX F9 : Starlink v0.9 : May 23, 2019 - DISCUSSION

[Lars-J]

Once the 60 sats are spread out in an orbital plane, they should be far less noticeable.

In retrospect, 60 of them in a tight formation being that visible is not surprising. (We can see distant star clusters but their individual stars would not be visible)

[Chris Bergin]

I won't stand for sobbing astronomy fans accusing Elon of lying on this forum. There's plenty of astronomy forums flapping over this. No need to bring it here.

[Danderman]

Once the 60 sats are spread out in an orbital plane, they should be far less noticeable.

In retrospect, 60 of them in a tight formation being that visible is not surprising. (We can see distant star clusters but their individual stars would not be visible)

On what basis are you stating that these satellites will operate in a single orbital plane?

[docmordrid]

A different take.

Jonathan McDowell ✓ @planet4589 (Harvard-Smithsonian Center for Astrophysics)

I think the magnitudes in this thread are grossly exaggerated though; as I said earlier, the very bright mags reported on the first night are probably clumps of satellites close together

https://twitter.com/planet4589/status/1132672683974549505
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So the good news: it seems that once the Starlink sats point their solar panels at the Sun properly they are significantly fainter (more like mag 5 than mag 2). That is still brighter than we had expected and still a problem, but somewhat less of a sky-is-on-fire problem.

https://twitter.com/planet4589/status/1132723102805299201

[mlindner]

I just want to mention that this satellite deployment I was surprised it worked. When my team launched a cubesat it ended up being stuck to another cubesat (recontact after deployment) and the TLE for it now mentions it has being named after both satellites. I'm surprised the satellites actually separated from each other rather than welding to each other.

[speedevil]

A different take.

Jonathan McDowell ✓ @planet4589 (Harvard-Smithsonian Center for Astrophysics)

I think the magnitudes in this thread are grossly exaggerated though; as I said earlier, the very bright mags reported on the first night are probably clumps of satellites close together

The solar panels are some 30m^2. This is some 6.6kW or so.
In actual operation, it seems plausible that they do not in fact require this amount of power, and considerable reserve is available to speed boost into orbit.
If in operation they put the solar panels so the lit face is oriented 45 degrees up, with the rear of the panel pointing at the darkside as they come over the sun-line, this would nearly eliminate sightings from the ground.
If the base plate is tilted -0.5 degrees away from the sun so it is shadowed by the front of the satellite, only that 3m*10cm or so part may be very visible, and that may be painted black.

If in fact they are in a boost configuration at maximum power at the moment of course.

Does anyone have any decent figures on aceleration?

We know the ISP is 1600s, this would with plausible efficiency put the thrust at some 60mN/kW.
We know the mass of the satellites is close to 250kg, so 3kW would put the thrust at 180mN, and the acceleration a hair under 1mm/s^2 (80m/s/day).
It seems plausible that they would be designed for constant thrust at 3kW, with ~2kWh (20kg of lithium-ion) of cyclic storage that can either be used for propulsion or comms.

My understanding is that to raise from 430 to 550km would take ~65m/s if it was an impulsive transfer, and ~120m/s if done continually.
The demonstrated thrust is a small fraction of this, as they'd be in the final orbit already - unless the initial altitude value I'm using is incorrect.

[launchwatcher]

The Starlink train just went directly overhead.  Getting nice and spread out now.  Few small clusters left but counted over 50 dots before I lost it to sunset on them.

Would post pictures but they just "fixed" the street light right in front of my house.  It went out and I never called about it because I hated it...someone called though...    Tried to take pictures but got nothing but orange sodium glare.  Something may have to happen to it again.....

Perhaps have a go at shorting out that streetlight in front of your house. Once you have put out that streetlight then have a second attempt at photographing the starlink train next time it passes over your area.

There are nondestructive approaches if the streetlight is controlled by a photocell:

https://petapixel.com/2015/02/19/a-laser-can-turn-off-streetlights-that-interfere-with-your-astrophotography/

Haven't tried this myself, use at your own risk, do not look into laser with remaining eyeball., etc., etc.,

[Semmel]

A different take.

Jonathan McDowell ✓ @planet4589 (Harvard-Smithsonian Center for Astrophysics)

I think the magnitudes in this thread are grossly exaggerated though; as I said earlier, the very bright mags reported on the first night are probably clumps of satellites close together

https://twitter.com/planet4589/status/1132672683974549505
|
|
So the good news: it seems that once the Starlink sats point their solar panels at the Sun properly they are significantly fainter (more like mag 5 than mag 2). That is still brighter than we had expected and still a problem, but somewhat less of a sky-is-on-fire problem.

https://twitter.com/planet4589/status/1132723102805299201

Really? Mag 5 is barely visible in my location and I was able to see the sats very clearly. Maybe my estimate of 2 to 3 (with 3 being darker) was exaggerated because they stand out so much due to their clustering and movement. I would love to see any decent measurement. It is also possible that I was at a lucky angle to the sun which allowed the illumination of their underside. I dont think I saw iridium-flare like solar panel reflections though. It would be interesting to know the true numer. Impressions can be deceptive.

[Mandella]

A different take.

Jonathan McDowell ✓ @planet4589 (Harvard-Smithsonian Center for Astrophysics)

I think the magnitudes in this thread are grossly exaggerated though; as I said earlier, the very bright mags reported on the first night are probably clumps of satellites close together

https://twitter.com/planet4589/status/1132672683974549505
|
|
So the good news: it seems that once the Starlink sats point their solar panels at the Sun properly they are significantly fainter (more like mag 5 than mag 2). That is still brighter than we had expected and still a problem, but somewhat less of a sky-is-on-fire problem.

https://twitter.com/planet4589/status/1132723102805299201

Really? Mag 5 is barely visible in my location and I was able to see the sats very clearly. Maybe my estimate of 2 to 3 (with 3 being darker) was exaggerated because they stand out so much due to their clustering and movement. I would love to see any decent measurement. It is also possible that I was at a lucky angle to the sun which allowed the illumination of their underside. I dont think I saw iridium-flare like solar panel reflections though. It would be interesting to know the true numer. Impressions can be deceptive.

I think the point is that once deployed into their proper orientation they will be mag 5. They are still heading out and are pointed all willy nilly now, thus the flashing mag 2.

[Nomadd]

The Starlink train just went directly overhead.  Getting nice and spread out now.  Few small clusters left but counted over 50 dots before I lost it to sunset on them.

Would post pictures but they just "fixed" the street light right in front of my house.  It went out and I never called about it because I hated it...someone called though...    Tried to take pictures but got nothing but orange sodium glare.  Something may have to happen to it again.....

Same thing happened to me. The funny thing is that it was the company who built and launched the Starlink sats that fixed the light.

[lonestriker]

I just want to mention that this satellite deployment I was surprised it worked. When my team launched a cubesat it ended up being stuck to another cubesat (recontact after deployment) and the TLE for it now mentions it has being named after both satellites. I'm surprised the satellites actually separated from each other rather than welding to each other.

Two things probably helped Starlink:

* The flat-spin prior to releasing the entire stack of satellites.  I can't remember ever seeing/hearing of this deployment mechanism.  Even if with recontact, unless they're physically stuck together, they should separate over time.
* Starlink being designed specifically for recontact as part of the standard deployment.  Seems like the Starlink satellites are a bit more robust than industry standard given how they removed the acoustic tiles inside the fairing.

[TorenAltair]

Yeah, great. Forgot to look yesterday, but caught them now, nearly directly overhead in Southern Germany. Some were occasionally brighter than ?Venus? further south. Only my neck suffered *g* Have to look for a better position the next days.

[Elthiryel]

I have just seen them passing for the third time and for the majority of time they were around 4.5 mag (rough estimation compared to nearby visible stars). Most of them flared in one point in the sky, that was roughly 2-3 mag, and there was one much brighter flare (maybe 0? hard to tell). However, the flare brightness depends on your exact location (similarly to the Iridium flares), my friends report that each of them flared very brightly when passing through one point in the sky one by one.

[Lars-J]

Once the 60 sats are spread out in an orbital plane, they should be far less noticeable.

In retrospect, 60 of them in a tight formation being that visible is not surprising. (We can see distant star clusters but their individual stars would not be visible)

On what basis are you stating that these satellites will operate in a single orbital plane?

The final constellation will have 60-70 sats per orbital plane, that’s why it is a reasonable assumption.

Granted this early production test phase might include some of them slowly phasing to another plane.

But once this test phase is over, single launches should indeed populate a single plane. It is the most efficient way to deploy a constellation of this size.

[ulm_atms]

The photo cell faces straight up.....    That's why I was happy when it went out...no way to fool it off.  And if I took a bb gun to it....they would..um...know 

Does anyone know if SpaceX has made contact with any of them yet?

[gongora]

Space-Track.Org has TLEs for 2019-029A through 2019-029AC now, so about half of them.

[ThomasGadd]

Once the 60 sats are spread out in an orbital plane, they should be far less noticeable.

In retrospect, 60 of them in a tight formation being that visible is not surprising. (We can see distant star clusters but their individual stars would not be visible)

On what basis are you stating that these satellites will operate in a single orbital plane?

The final constellation will have 60-70 sats per orbital plane, that’s why it is a reasonable assumption.

Granted this early production test phase might include some of them slowly phasing to another plane.

But once this test phase is over, single launches should indeed populate a single plane. It is the most efficient way to deploy a constellation of this size.

I agree it is more efficient to deploy the satellites into single planes per launch. 

Say you need half the planes populated for minimum operation 12 launches.

There is a minimum number that is enough to be operational if we they divide across 2 planes that's 6 launches or 3 planes that's 4 launches that saves a lot a time for a minimally operational constellation.
Time is more important cost that the moment.

SpaceX has run the numbers and I am looking the the next launches.

[punder]

Just saw them over Colorado Springs! WOW!

A string of several sats, not very far apart, followed by a few more at larger distances. Fantastic.

Used satflare.com.

[pmonta]

Starlink trails from a 60-second exposure.  This was taken with iTelescope's T11 telescope about 15 minutes ago.  I believe the trails starting at upper left are from the "leaders".

I can put the FITS somewhere so that photometry can be done.

[Zed_Noir]

I just want to mention that this satellite deployment I was surprised it worked. When my team launched a cubesat it ended up being stuck to another cubesat (recontact after deployment) and the TLE for it now mentions it has being named after both satellites. I'm surprised the satellites actually separated from each other rather than welding to each other.

Two things probably helped Starlink:

* The flat-spin prior to releasing the entire stack of satellites.  I can't remember ever seeing/hearing of this deployment mechanism.  Even if with recontact, unless they're physically stuck together, they should separate over time.
* Starlink being designed specifically for recontact as part of the standard deployment.  Seems like the Starlink satellites are a bit more robust than industry standard given how they removed the acoustic tiles inside the fairing.

Also that each Starlink bird got attitude control Krypton ion thrusters (aka the Superman repellent sprays ). Something most Cubesats lacks.