170 replies to this topic

[GUNER]

I just viewed a video of the first batch of 60 STARLINK satellites at these links:

  http://www.spaceweather.com/

 https://www.youtube....eature=youtu.be

 

  From what I could find the STARLINK system is going to eventually have 2800 satellites @ 710 miles, 1600 @ 340 miles, & 7500 @ 210 miles.  If this is what the first batch of 60 looks like what are the night skies going to look like when there are 12,000 of them up there?  Will there be a negative impact on astrophotography?

[WarmWeatherGuy]

They can't be seen when they're in the Earth shadow. The ISS can't be seen much after and hour after sunset but these guys are a bit higher. It can certainly shrink the time window around midnight that low satellites can ruin pictures. While being higher allows them to be seen longer into the evening they will also be less bright due to the increased distance.

[RadioAstronomer]

I'm worried about their impact on professional astronomy and more specifically on the surveys that work under the NASA Planetary Defense Coordination Office (Panstarrs, Catalina...)

Edited by RadioAstronomer, 25 May 2019 - 11:12 AM.

[t_image]

I just viewed a video of the first batch of 60 STARLINK satellites at these links:

  http://www.spaceweather.com/

 https://www.youtube....eature=youtu.be

 

  From what I could find the STARLINK system is going to eventually have 2800 satellites @ 710 miles, 1600 @ 340 miles, & 7500 @ 210 miles.  If this is what the first batch of 60 looks like what are the night skies going to look like when there are 12,000 of them up there?  Will there be a negative impact on astrophotography?

So you've done some research that gives more context to the situation, seeing there is planned 3 orbital shell layers!!

It is a good question. As someone who regular intentionally seeks to image and capture satellites in video, I still am wondering.

 

I caught the Starlink sats as well on video, posted in this thread:

https://www.cloudyni...lites-on-video/

 

If I have another chance soon, I'll intentionally try to figure out the general magnitude via comparing with stars at extinguishing/appearing given altered exposure settings of the video....

From the footage I shot, it looks like they were magnitude ~4.5-5, at 450km altitude..

 

Note they are all bunched together until they individual space themselves apart in the orbital plane they were launched in (final placement)...

It's easier to be disturbed by a bunch than one mag. 5 satellite passing over...

 

I'd say the lower orbits will be brighter, but have fewer reflection timing and will pass across faster. The higher orbits will be fainter but take longer to pass through.

Since something of this scale hasn't been done before, it is hard to say.  The key operative factor is not the typical brightness but the scale of numbers that raises the chances of "photobombing."

Consider there were only 72 Iridium comm satellites, at ~780km. They usually were at ~7-8 magnitude normally. A few were good for "Iridium Flare" events regularly.... Now consider the sheer numbers of Starlinks, plus the other large constellations the competitors are going to put up there(One Web, Telesat, Amazon)...

 

We'll see. Like it or not.

 

The good thing is all these objects are predictable and with adequate planning one can take images with certainty there will be no stragglers passing through a shot at a given time/location (one point of the website Calsky.com).

With airplanes, one doesn't have that option.....

[Stellar1]

Who knows really, there outta be a law, i don't get it, so there will be internet all around the world in every corner. YAY!! we can all stay up to date on the Kardashians while were vacationing in the Serengeti, 

cause who cares about lions and elephants right!? CAPITAL GAIN is the goal here, and NOT internet service.

[MikeTahtib]

Could we start a grass-roots movement to have them painted flat black?   Or are there thermal issues? 

[cfosterstars]

With pixinsight, I dont really see any impact to satellite trails or even most aircraft trails. As long as there are at least a subset of subs that are free of artifacts, LocalNornalization and large scale pixel rejection just get rid of them and the rest of the data from those subs is quite useable.

 

THis is another good argument for CMOS cameras with low read noise so you dont need really long exposures and take more subframes. That gives more good frames for the clean reference image for LocalNormalization. 

Edited by cfosterstars, 25 May 2019 - 12:01 PM.

[Darren in Tacoma]

To me the impact would be more on visual astronomy. I could see satellite trails ruining some single frame shots like meteor showers or Milky Way stuff, but I really don't want to enjoy the night sky by staying up late and watching the satellites with my friends.

[RedLionNJ]

I don't really perceive such a set of small satellites as being much of a negative at all.

 

For most imaging, sigma-kappa stacking will reject outliers like passing satellites (if they're even visible in frames).

 

For visual - might actually be kind of cool for a while, depending on how closely they're stacked in their orbits.

[pfile]

interesting twitter thread here:

 

https://twitter.com/...163931378610178

 

short story - modeling the full constellation = at least 500 satellites directly illuminated by the sun at seattle's latitude @ midsummer midnight. surprised by that given the low orbit but the poster is a planetary astronomer...

 

rob

[lakeorion]

More junk in the sky for grumps like me to grump about.

[Francois]

Yeah, so there's only a few things to worry about here:

• satellites directly illuminated by the sun, which will be during dawn/dusk and west/east, as noted mag ~4.5. At 550km altitude this will happen until the satellite is 22 degrees away from the terminator, at which point the sun is below the satellite horizon, 18 degrees for the lower 350km constellation. For reference, dawn/dusk is generally considered to be 18 degrees from the terminator so 4 degrees extra to get a Starlink-free meridian.
• satellites illuminated by atmospheric scattering, same as above but much fainter and lasting longer
• satellites directly illuminated by the moon, which is going to be a problem when the moon is visible (and slightly before/after with the same angles as for the sun) and ~14 mags dimmer than sun illumination (depending on moon phase).

So, it's basically only a problem when you already had problems, either dawn, dusk, or moon. Dark satellites will be much dimmer than skyglow, and all professional surveys already do trail detection.

 

The real problem is going to be for people that can view the North/South maximum latitude of the orbits, at 53, 46, and 42 degrees for the 350km sats (if memory serves, the FCC filings server is down). Sites that can see those will have a band of no-go declination, where there will almost always be satellites. That's going to be a problem in Canada, Europe, and Russia.

[pfile]

yes - i guess it is the sheer number of these things that has caused so much consternation. seems like there's on the order of 5000 satellites currently in orbit? adding 12,000 more (eventually) seems like a pretty big change.

 

rob

[Francois]

yes - i guess it is the sheer number of these things that has caused so much consternation. seems like there's on the order of 5000 satellites currently in orbit? adding 12,000 more (eventually) seems like a pretty big change.

 

rob

Not all satellites are the same. Altitude makes a huge difference.

[pfile]

so apparently enough professional observational astronomers complained on twitter about this and now musk is at least saying that he's asked the spacex engineers to study how to lower the albedo of the starlink satellites.

 

rob

[Jon Rista]

so apparently enough professional observational astronomers complained on twitter about this and now musk is at least saying that he's asked the spacex engineers to study how to lower the albedo of the starlink satellites.

 

rob

So, even with low albedo...what happens when one of these things, even if it is effectively "dark", passes in front of a star that is being studied...say to determine if it has an exoplanet? Now the star will dim due to one of tens of thousands of satellites passing in front of it, in addition to an exoplanet passing in front of it. And how many other scientific endeavors can be "screwed with" due to tens of thousands of new satellites being tossed into orbit so that: we can have internet at the poles...

 

I also wonder...how will tens of thousands of additional satellites affect the launch of space craft to, say, get to the moon to build a lunar base, or send a manned mission to mars? How many launch windows that might otherwise have been viable will now have to be scrubbed because there are so many satellites zipping around in orbit so that: we can have internet at the poles...

 

I feel there has been a severe lack of real consideration of the consequences of putting so many satellites (not just StarLink, but others such as OneWeb (which will orbit at 1200km!), etc.) into LEO...

Edited by Jon Rista, 27 May 2019 - 03:13 PM.

[vdb]

This whole thing started out as a rich mans competition just for ego's sake ... by the time this evers becomes operational, ground based solutions will have reached most parts of the world, and one can ask themselves if we need to be connected even at the most desolate places anyway.

 

/Yves

[Francois]

so apparently enough professional observational astronomers complained on twitter about this and now musk is at least saying that he's asked the spacex engineers to study how to lower the albedo of the starlink satellites.

 

rob

Yeah, no. Thermal management is a huge issue for anything in the inner solar system. Solar irradiance is 1kW/m², and over a satellite's body that's a lot more than the thermal losses from various equipment. That's why most satellites are wrapped in MLI, are ultra-white, or have a reflective finish except for surfaces that need to see the sky. Otherwise the satellite heats up.

 

Besides, they've been talking with various astronomers (mostly radio folk from NRAO and ATNF) for years.

[WarmWeatherGuy]

The two-line orbital elements are now available from NORAD/CelesTrak. They will be visible the next few evenings and mornings. I was able to see them in Stellarium by selecting tle-new. I didn't see starlink as an option in Stellarium. In Stellarium use Alt-Z to select and update the ones you want to see.

[WarmWeatherGuy]

When the satellites begin providing internet service they will forever ruin Earthbound radio astronomy in the microwave band.

[Francois]

When the satellites begin providing internet service they will forever ruin Earthbound radio astronomy in the microwave band.

Only in selected bands, namely 10.7-12.7GHz, 12.15-12.25GHz, 12.75-13.25GHz, 14-14.5GHz, 17.8-18.6GHz, 18.8-19.3GHz, 19.7-20.2GHz, 27.5-29.1GHz, and 29.5-30GHz. They are forbidden from emitting in 14.47-14.5GHz (the formaldehyde line) to protect radio astronomy, and must coordinate with radio observatories when using the 10.7-11.7GHz band.

 

The SKA is at 14GHz and lower and is largely unaffected. For CMB work it's all above 90GHz and they're also unaffected. Current X, Ku, and K-band users will sure be ****, but it's not all doom-and-gloom.

[WarmWeatherGuy]

60 Skylink + 4 Skylink debris satellites flew overhead last night. I only saw a few of them and they were bright. My camera caught several more that I missed even with binoculars. Most were not even visible to the camera. These things are supposed to be desk shaped like the obelisk in 2001 A Space Odyssey. It seems that they flash like the iridium flares. When the angle relative to you, it, and the sun are just right it can be very bright, otherwise it is very dim.

 

 

 

 

[Konihlav]

the answer is clear and short.

 

Definitively yes. This will have a huge negative impact.

 

It will have a huge impact on all of us. Only those with tiny FOV (small format cameras and few meters long focal length scopes) may be OK with that.

Others will be negatively impacted.

Mostly TWAN style photographers.

 

BTW if you have a lot of $$$ you can do everything! It may sound surprising to some, but, unfortunately, it's very true

[Francois]

Once again: they will not have an effect after dusk and before dawn. MEO satellites are the real problem for satellite trails. This isn't magic, they need to be illuminated to reflect light.

[DSO_Viewer]

Yeah, so there's only a few things to worry about here:

• satellites directly illuminated by the sun, which will be during dawn/dusk and west/east, as noted mag ~4.5. At 550km altitude this will happen until the satellite is 22 degrees away from the terminator, at which point the sun is below the satellite horizon, 18 degrees for the lower 350km constellation. For reference, dawn/dusk is generally considered to be 18 degrees from the terminator so 4 degrees extra to get a Starlink-free meridian.
• satellites illuminated by atmospheric scattering, same as above but much fainter and lasting longer
• satellites directly illuminated by the moon, which is going to be a problem when the moon is visible (and slightly before/after with the same angles as for the sun) and ~14 mags dimmer than sun illumination (depending on moon phase).

So, it's basically only a problem when you already had problems, either dawn, dusk, or moon. Dark satellites will be much dimmer than skyglow, and all professional surveys already do trail detection.

 

The real problem is going to be for people that can view the North/South maximum latitude of the orbits, at 53, 46, and 42 degrees for the 350km sats (if memory serves, the FCC filings server is down). Sites that can see those will have a band of no-go declination, where there will almost always be satellites. That's going to be a problem in Canada, Europe, and Russia.

No some of the Northern States will suffer also.

 

Steve