SpaceX F9: Starlink v1 Flight 1 : November 11, 2019 - DISCUSSION

[Robotbeat]

I tried to model the reentry of deployment debris from this Starlink launch
using the tracking data from reddit.
The result is on the attached graph, looks like reentry could be some days around Christmas.

But I've never done this before, so -
QUESTION:
Is this estimate - reasonable ?

Way too fast.
Taking the decay shown in the first 7days, and assuming nothing interesting happens on the Solar and Geomagnetic front... We are looking at about 102-105 days to reentry. This puts it around 22 feb.

Decay isn’t linear, but you’re taking that into account, right?

[woods170]

Several planes old and new are close enough to use.  SpaceX wants to populate US orbits first if possible.

What’s a US orbit?

US orbits refers to a range of inclinations covering CONUS.
Naturally that set of inclinations covers not JUST the CONtinental United States.

[CyndyC]

I tried to model the reentry of deployment debris from this Starlink launch
using the tracking data from reddit.
The result is on the attached graph, looks like reentry could be some days around Christmas.

But I've never done this before, so -
QUESTION:
Is this estimate - reasonable ?

Way too fast.
Taking the decay shown in the first 7days, and assuming nothing interesting happens on the Solar and Geomagnetic front... We are looking at about 102-105 days to reentry. This puts it around 22 feb.

I don't think solar activity's contribution to drag can realistically be zeroed out of any predictions. I've been getting weekly space weather forecast emails from NOAA's Space Weather Prediction Center for many years. I believe we're at a solar minimum in the 11-year solar cycle, meaning less sunspots to interfere with radio communications, but more coronal holes. Those are low density open magnetic fields that allow high speed solar winds to escape.

Lately there have been a lot of weeks with G-1 and G-2 geomagnetic storms of the 5 levels, with every other to every third week completely quiet. I can't remember the last time I saw a G-3, but I've seen those too. G-1 has minor impact on satellites, but G-2 and G-3 can require corrective action.

From the page about satellite drag at https://www.swpc.noaa.gov/impacts/satellite-drag

When the Sun is quiet, satellites in LEO have to boost their orbits about four times per year to make up for atmospheric drag. When solar activity is at its greatest over the 11-year solar cycle, satellites may have to be maneuvered every 2-3 weeks to maintain their orbit [1].

In addition to these long-term changes in upper atmospheric temperature and density caused by the solar cycle, interactions between the solar wind and the Earth’s magnetic field during geomagnetic storms can produce large short-term increases in upper atmosphere temperature and density, increasing drag on satellites and changing their orbits.

The scales and their effects can be found at https://www.swpc.noaa.gov/noaa-scales-explanation

[gongora]

All of the planes in the initial build out are at the same inclination.  They all cover the U.S.  I would think spacing the deployments so that the filled planes are somewhat evenly spaced after 10 or so launches would be good.

As for whether some of these sit at 350km for a while, it may depend on whether SpaceX thinks they'll get approval for the modified constellation architecture anytime soon.  It just wasn't filed soon enough before this launch to have any chance of approval yet.  Despite the strange wording of the partially granted STA for this mission, I assume they can raise all of these satellites to the previously approved orbits.

[CyndyC]

Several planes old and new are close enough to use.  SpaceX wants to populate US orbits first if possible.

What’s a US orbit?

US orbits refers to a range of inclinations covering CONUS.
Naturally that set of inclinations covers not JUST the CONtinental United States.

Are you familiar with planes in the 53 degree orbit that would provide more coverage of the US than others?

I suspect someone has misinterpreted a statement from SpaceX.

The 53rd parallel north is a little up there for starting US coverage if that's what you meant, but one of the SpaceX goals with Starlink is to serve under served areas, which is a good goal to start with while still testing and improving on operations.

In addition, I came across something very intriguing in a search for images of the 53rd parallel. If I'm interpreting a particular post and image correctly in a community for users of the game series Sim City, with which players plan and construct cities, so a game Elon Musk is likely to have explored, the 53rd parallel is used as a virtual "equator". Coincidence? You decide...

http://www.modthesims.info/d/596138/mid-latitude-sunrise-sunset-offset-times.html

[TripleSeven]

Several planes old and new are close enough to use.  SpaceX wants to populate US orbits first if possible.

What’s a US orbit?

US orbits refers to a range of inclinations covering CONUS.
Naturally that set of inclinations covers not JUST the CONtinental United States.

Are you familiar with planes in the 53 degree orbit that would provide more coverage of the US than others?

I suspect someone has misinterpreted a statement from SpaceX.

The 53rd parallel north is a little up there for starting US coverage if that's what you meant, but one of the SpaceX goals with Starlink is to serve under served areas, which is a good goal to start with while still testing and improving on operations.

In addition, I came across something very intriguing in a search for images of the 53rd parallel. If I'm interpreting a particular post and image correctly in a community for users of the game series Sim City, with which players plan and construct cities, so a game Elon Musk is likely to have explored, the 53rd parallel is used as a virtual "equator". Coincidence? You decide...

http://www.modthesims.info/d/596138/mid-latitude-sunrise-sunset-offset-times.html

latitude and inclination are not the same

[CyndyC]

latitude and inclination are not the same

ok, then where is a 53 degree inclination? With respect to latitudes?

[gongora]

latitude and inclination are not the same

ok, then where is a 53 degree inclination? With respect to latitudes?

It goes between 53 north and 53 south.

[su27k]

Several planes old and new are close enough to use.  SpaceX wants to populate US orbits first if possible.

What’s a US orbit?

US orbits refers to a range of inclinations covering CONUS.
Naturally that set of inclinations covers not JUST the CONtinental United States.

Are you familiar with planes in the 53 degree orbit that would provide more coverage of the US than others?

I suspect someone has misinterpreted a statement from SpaceX.

"US orbit" is not accurate, I assume he was referring to the new planes. SpaceX requested FCC to change the number of planes for the 550km shell, from 24 planes to 72 planes, they think this will allow them to cover US more quickly, using one launch to populate 3 nearby planes. See this thread for details from SpaceX filing.

[Danderman]

Several planes old and new are close enough to use.  SpaceX wants to populate US orbits first if possible.

What’s a US orbit?

US orbits refers to a range of inclinations covering CONUS.
Naturally that set of inclinations covers not JUST the CONtinental United States.

Are you familiar with planes in the 53 degree orbit that would provide more coverage of the US than others?

I suspect someone has misinterpreted a statement from SpaceX.

"US orbit" is not accurate, I assume he was referring to the new planes. SpaceX requested FCC to change the number of planes for the 550km shell, from 24 planes to 72 planes, they think this will allow them to cover US more quickly, using one launch to populate 3 nearby planes. See this thread for details from SpaceX filing.

If the US would be covered more quickly using more planes, then everywhere on the planet between 53 degrees N and S would likewise be covered more quickly. Unless you are suggesting that SpaceX can magically cover certain longitudes more frequently than others.

I just to make sure that nobody here thinks that “US orbits” are a thing.

[CorvusCorax]

That being said, these sats do spend most of their time near the exreme latitudes of their orbits than near the equator, so a certain mix of orbits and planes can create 2 "bands of full coverage" - lets say between 20° and 50° - both north and south - while the area further towards the poles would remain uncovered, and the coverage "in between" - aka over equatorial latitudes below 20° N/S would be too sparse.

In the south, such a band would cover New Sealand, South Afrika, most of Chile, Argentina, Uruquay, the southern half of Australia,
and the southern tips of Brasil, Paraquay, Botswana, Namibia and Madagaskar in the south, among vast vast stretches of open ocean.

In the North it would cover the continental United States except Alaska, Central and Southern Europe, North Africa (Everything down to Northern half of Sahara) The Middle East, Iraq, Iran, Pakistan, Afghanistan, South of Kasachstan, the Northern third of India and the Himalayas, all of China, Korea and Japan.

Almost none of Russia though.

[envy887]

Several planes old and new are close enough to use.  SpaceX wants to populate US orbits first if possible.

What’s a US orbit?

US orbits refers to a range of inclinations covering CONUS.
Naturally that set of inclinations covers not JUST the CONtinental United States.

Are you familiar with planes in the 53 degree orbit that would provide more coverage of the US than others?

I suspect someone has misinterpreted a statement from SpaceX.

"US orbit" is not accurate, I assume he was referring to the new planes. SpaceX requested FCC to change the number of planes for the 550km shell, from 24 planes to 72 planes, they think this will allow them to cover US more quickly, using one launch to populate 3 nearby planes. See this thread for details from SpaceX filing.

If the US would be covered more quickly using more planes, then everywhere on the planet between 53 degrees N and S would likewise be covered more quickly. Unless you are suggesting that SpaceX can magically cover certain longitudes more frequently than others.

I just to make sure that nobody here thinks that “US orbits” are a thing.

Not "everywhere" else between 53N and 53S. With a limited number of satellites and planes, it's possible to get complete coverage at CONUS latitudes of 40-50 degrees (and the corresponding southern latitudes) while leaving the equatorial regions with only very intermittent coverage. This is the minimum viable constellation to service the US, and it's what SpaceX plans to fill first.

This minimum constellation also covers southern Canada and parts of Australia pretty well, so SpaceX is also filing for regulatory permission to broadcast into those areas.

Since longitude is obviously irrelevant, they could also cover southern Europe, parts of Asia, southern South America, etc, but the regulatory issues will IMO take longer to sort out in those places so the limiting factors there will be things other than coverage.

[ThomasGadd]

SpaceX has applied to the FCC for permission to restructure this initial shell of the constellation from 24 planes to 72 planes.  They have not yet gotten permission to do that.  They would like to split the satellites from this launch into 3 of the 72 planes.  Right now they have permission to raise 20 of them into one of the 24 planes that are currently approved.  Where the rest of them end up may depend on further developments with their modification request.

What does that mean, in terms of deployment of the satellites? Are the 40 satellites going to sit at 350 km until this is resolved?

Several planes old and new are close enough to use.  SpaceX wants to populate US orbits first if possible.

What I meant and should have said is. 

The orbits covering US deployment first. 

[Comga]

I tried to model the reentry of deployment debris from this Starlink launch
using the tracking data from reddit.
The result is on the attached graph, looks like reentry could be some days around Christmas.

But I've never done this before, so -
QUESTION:
Is this estimate - reasonable ?

This looks reasonable to me.
If you used a scale height of 20 km for the doubling of exoatmospheric density, a good rule of thumb I believe, the time to descend 20 km is half the lifetime. That is, every time the orbit decays by 20 km the descent rate would double. I had pretty good correspondence with the descent of the Chinese Tiongong-1 (sp?) with that rule.
The graph  puts half the life at about 25 km descent so it’s reasonable. A bit longer than indicated by my rule of thumb, but reasonable.

[Danderman]

This stuff is harder than it looks because most people never think of the end user experience, as this interim US coverage brings up a lot of issues that no one here is discussing.

Unless the constellation provides continuous coverage for all users, and has full inter satellite links, there would have to be significant work arounds to provide useful benefits for customers.

[gongora]

This stuff is harder than it looks because most people never think of the end user experience, as this interim US coverage brings up a lot of issues that no one here is discussing.

Unless the constellation provides continuous coverage for all users, and has full inter satellite links, there would have to be significant work arounds to provide useful benefits for customers.

These things have been discussed in the Starlink Discussion threads.

[Danderman]

I was wrong.

Every orbit provides more coverage to higher latitudes than Equatorial regions.

That doesn't mean that are architectures in a 53 degree constellation that favor US coverage, but there is a number of satellites where the US is fully covered, but Brazil is not. Of course, if the US is covered, so is the North Pacific or China.

[AC in NC]

I was wrong.

Every orbit provides more coverage to higher latitudes than Equatorial regions.

That doesn't mean that are architectures in a 53 degree constellation that favor US coverage, but there is a number of satellites where the US is fully covered, but Brazil is not. Of course, if the US is covered, so is the North Pacific or China.

Kudos for that concession.

Would it seem unappreciative if I asked you to take one step further and accept ground stations and regulatory environment (in a loose sense) as integral components of architecture?  Absent ISL, that North Pacific or China "coverage" is meaningless without ground stations.

[Mandella]

Just going to make the point that a substantial area of the US is below the initial rollout latitude of 40 North, including me. As I understood it a major reason they are requesting more planes is to hasten the usable coverage into the southern states.

Purely from self interest I hope they get speedy approval.

[gongora]

Under the currently approved plan it kinda looks like they'd fill about every fourth plane of the 24 planes for initial service, then expand it to cover approximately every other plane (v1 sats in 11 planes and v0.9 in one plane?) to cover the rest of CONUS.  I'm not sure how that translates to the newer orbital scheme.