SpaceX F9 : Starlink Group 2-1 : VSFB SLC-4E : 13/14 September 2021 (03:55 UTC)

[klod]

In that case, it’s entirely possible that another drone ship has been leased and modified at a west coast or Asia-Pacific shipyard.

Hm, it makes more sense in order to accomplish this launch in time. Has never thought about leasing a droneship.

[gongora]

This flight is NET July.  It could happen later if the necessary equipment isn't ready on the west coast.

[Kiwi53]

But it would seem a bit strange for SpaceX to move a booster to the West coast and then not use it for weeks or months because the barge we've all assumed is ASOG is still being built and can't be in California waters until after the northern summer.

Jansen's speculation that there may be another unnoticed barge under conversion somewhere else is intriguing.

[gongora]

Who said ASOG is going to the west coast?  The obvious choice would be OCISLY.  Maybe they live with a slower flight rate on the east coast in July if they want to ship an existing ASDS out to California after the current flurry of flights.

[zubenelgenubi]

A bit strange that they're starting on the 70 degree shell. I'd expect the polar orbit shell to go first so that they can claim world-wide coverage.

Maybe lasers are not yet ready?

I >guess< coverage from the satellites in a 70 deg inclined orbit are enough for virtually the entire world population--excepting Santa Claus' crew and the realm of Emperor Mumble Happyfeet.

[Robotbeat]

Well, technically, you could still see the Starlink satellites at 70 degrees inclination and 540km (roughly?) peak up above the horizon if you were at the North pole. In fact, at 540km altitude, they could be as low as almost 67 degrees (67.212deg roughly) and still get to the horizon at the North Pole. But, it'd only be briefly.

So if you put your antenna on a tall pole and they put enough satellites at 70 degrees latitude, maybe it'd work.

(But I think they'd need an FCC modification if they wanted to transmit at such an extreme angle.)

[OneSpeed]

Those coordinates actually give exactly 70°

I measure about the same, but the S1 time of flight is about 08:35, in which time the earth rotates by about 2.15°. The ASDS recovery location is at about 29.36° north. In the flight time it will move east by about 207km. So, the inclination of the S1 trajectory is much less than 70°, somewhere around 55° from the map. I don't think you can assume that this angle is the same as the orbital inclination of the payload.

However, it is possible to calculate the launch azimuth including the earth's rotation. From https://www.orbiterwiki.org/wiki/Launch_Azimuth, you can use β = asin(cos(mi)/cos(ϕ)) and then apply Vorbital = Vinertial - Vearth.

Azimuth is measured from North (or South), so that 70° angle is actually a launch azimuth of 20°. Using a small app I wrote, and assuming an orbital injection at 167km altitude, the resultant orbital inclination would be 71.5375°. Using Jansen's figure of 69.85°, or rather a launch azimuth of 20.15°, I get an orbital inclination of 71.4195°.

Neither of these values exactly match any of the polar tranche inclinations, so I'm not sure what's going on here.

[Orbiter]

I think F9 Starlink missions might dogleg slightly on second stage ascent. I've found the ASDS locations for missions out of the Cape would imply a 51.25 degree inclination orbit instead of the 53.00 degree one we know they end up in. That dogleg should bring the second stage inclination down from the ~71.42 you've calculated to about 70.00 degrees even.

[OneSpeed]

I think F9 Starlink missions might dogleg slightly on second stage ascent. I've found the ASDS locations for missions out of the Cape would imply a 51.25 degree inclination orbit instead of the 53.00 degree one we know they end up in. That dogleg should bring the second stage inclination down from the ~71.42 you've calculated to about 70.00 degrees even.

It is not so much a dogleg (which would be inefficient) as pointing a couple of degrees further north for the entire boost phase(S1 and S2) to compensate for the rotation of the earth.

Starlink to 53° is quite similar to Dragon to the ISS, which is at 51.6°. There is a worked example at https://www.orbiterwiki.org/wiki/Launch_Azimuth, and I get a very similar result for Dragon (42.77°), only different because I am using an injection altitude of 196km, vs their 300km (42.76°). The difference between the inertial and orbital azimuths is about 2.2°, more than the difference you are seeing in the inertial ground track from Google Maps.

Again, there is no direct relationship between the inertial ground track of the booster and the orbital inclination of the satellite, unless it is an equatorial launch, or from one of the poles. Otherwise, you need to account for the rotation of the Earth.

Either way, this might not be the right thread to discuss this, perhaps a mod could suggest the best place.

[LouScheffer]

A bit strange that they're starting on the 70 degree shell. I'd expect the polar orbit shell to go first so that they can claim world-wide coverage.

Maybe lasers are not yet ready?

I >guess< coverage from the satellites in a 70 deg inclined orbit are enough for virtually the entire world population--excepting Santa Claus' crew and the realm of Emperor Mumble Happyfeet.

Seems reasonable.  70 degrees is well above the arctic circle at 66.5 degrees, and according to Wikipedia, only 4 million people total live within the Arctic circle (and presumably the majority of these are near the southern edge).  So 70 degrees likely covers 99.99% of the world's population.

Furthermore, the northmost point of Alaska is at a little less than 72 degrees, so a 70 degree orbit lets them claim to cover the entire United States.

A counter-argument might exist if a large customer (such as the military) was willing to pay good money for 100% coverage.

[Lars-J]

Yes 70 degrees covers 99.9% (or more) of all residential/fixed customers… but there is a significant customer of polar internet access: long haul commercial aviation where the shortest route is near polar. (Plus the military customer of course)

Since they have already launched some polar Starlinks, do we know for sure that this launch targets 70 degrees instead of polar/SSO?

[zubenelgenubi]

Who said ASOG is going to the west coast?  The obvious choice would be OCISLY.  Maybe they live with a slower flight rate on the east coast in July if they want to ship an existing ASDS out to California after the current flurry of flights.

Cross-post:

https://nextspaceflight.com/launches/details/5333

Starlink V1 L29
Launch Time
NET July, 2021
Location
SLC-40 or LC-39A, Florida, USA

"Only" four Falcon 9 launches planned in June!

OCISLY transits to the Pacific after catching and returning the SpX-22 first stage?

More here in the manifest discussion thread.

[macpacheco]

Yes 70 degrees covers 99.9% (or more) of all residential/fixed customers… but there is a significant customer of polar internet access: long haul commercial aviation where the shortest route is near polar. (Plus the military customer of course)

Since they have already launched some polar Starlinks, do we know for sure that this launch targets 70 degrees instead of polar/SSO?

However its important to realize that long haul aircraft typically fly above 30000ft. This allows them line of sight with satellites @ 450km quite farther away than somebody on the ground with 100% flat terrain. I don't know how far Starlink terminals can talk to Starlink satellites due to attenuation and atmospheric effects.
If the issue is solely air traffic, it *might* be possible to talk to a Starlink satellite 1500 km away. No, I didn't do any math.
In the same way, a ship in the middle of the ocean, with a starlink antenna mounted 30m above SL can talk to satellites perhaps 800km away. Again, I didn't do any math.
Just pointing out that we don't know the limits of the Starlink system. And a ground customer is uneven terrain, a sea going customer and an airborne customers have very different views of the sky.
Just hoping somebody would do the math, while respecting the fact we don't know how far Starlink satellite can talk to Starlink terminal.

[DistantTemple]

Yes 70 degrees covers 99.9% (or more) of all residential/fixed customers… but there is a significant customer of polar internet access: long haul commercial aviation where the shortest route is near polar. (Plus the military customer of course)

Since they have already launched some polar Starlinks, do we know for sure that this launch targets 70 degrees instead of polar/SSO?

However its important to realize that long haul aircraft typically fly above 30000ft. This allows them line of sight with satellites @ 450km quite farther away than somebody on the ground with 100% flat terrain. I don't know how far Starlink terminals can talk to Starlink satellites due to attenuation and atmospheric effects.
If the issue is solely air traffic, it *might* be possible to talk to a Starlink satellite 1500 km away. No, I didn't do any math.
In the same way, a ship in the middle of the ocean, with a starlink antenna mounted 30m above SL can talk to satellites perhaps 800km away. Again, I didn't do any math.
Just pointing out that we don't know the limits of the Starlink system. And a ground customer is uneven terrain, a sea going customer and an airborne customers have very different views of the sky.
Just hoping somebody would do the math, while respecting the fact we don't know how far Starlink satellite can talk to Starlink terminal.

Assuming (I am confident this is correct!) that the 25degrees minimum elevation of signal is still relevant to communicating with aircraft, your argument will not give any greater corridor width beside the satellite orbit than what has been discussed for a ground customer, as the 25 degrees is the determining factor, not being out of sight due to the earths curvature.

[LouScheffer]

Yes 70 degrees covers 99.9% (or more) of all residential/fixed customers… but there is a significant customer of polar internet access: long haul commercial aviation where the shortest route is near polar. (Plus the military customer of course)

However its important to realize that long haul aircraft typically fly above 30000ft. This allows them line of sight with satellites @ 450km quite farther away than somebody on the ground with 100% flat terrain.  [...]

Assuming (I am confident this is correct!) that the 25degrees minimum elevation of signal is still relevant to communicating with aircraft, your argument will not give any greater corridor width beside the satellite orbit than what has been discussed for a ground customer, as the 25 degrees is the determining factor, not being out of sight due to the earths curvature.

It's not clear the 25 degree limit will apply for an airplane.   This limit (or at least a portion of it) may well be from the user terminal array structure, which can only point a limited angle from the boresight. If this is the case, it could be solved with an antenna consisting of several phased arrays (perhaps a miniature version of the Pave Paws antenna below).   This would be cost prohibitive for user terminals but perhaps not for airplanes.

A second possible reason might to be to avoid interference with (or from) ground equipment.  This could be avoided in an airplane be restricting operation to altitudes above 3000 meters above ground, or similar.

A third reason might be if the satellite can only direct its beams a certain angle from straight down.  In this case the polar airplanes are out of luck.  Though they are high enough for line of sight to a satellite, the satellite cannot send a beam in their direction.

[zubenelgenubi]

Cross-post:

Multiple USA launch updates from SFN Launch Schedule, updated June 7

Falcon 9 / Starlink
Launch date: July
Launch time: TBD
Launch site: SLC-4E, Vandenberg Space Force Base, California

[Thunderscreech]

https://twitter.com/FccSpace/status/1405622587301023748?s=20

[Jansen]

0817-EX-ST-2021 Starlink RF Mission 1-5

This application uses information from previous grant 1379-EX-ST-2020. This STA is necessary to authorize launch vehicle communications for Starlink RF Mission 1-5 from SLC-4E, Vandenberg Air Force Base, and the experimental recovery operation following the Falcon 9 launch. The application includes sub-orbital first stage and orbital second stage. Trajectory data shall be provided directly to NTIA, USAF, and NASA. All downrange Earth stations are receive-only. The recovery portion is limited to two functions: 1) pre-launch checkout test of the command uplink from an onshore station at launch site, and 2) command of landed stage from recovery boat. All operations are pre-coordinated with the Launch Range. Launch licensing authority is FAA Office of Commercial Space Transportation.

Requested Period of Operation
Operation Start Date:   07/01/2021
Operation End Date:   01/01/2022

Grant approved
https://apps.fcc.gov/els/GetAtt.html?id=276390

[Jansen]

(PDF)

Possibly July 30, sounds about right.

[crandles57]

July 6 arrival. So July 12 for launch possible or likely some checkouts and a bit/lot tight to manage that?

(If next East coast Starlink launch is polar that can't be til 26rd July so this could point towards VSFB launch being 12th? and East coast being 30th.)