OHM Neil Gehrels Swift Observatory 260620

[BrianJ]

BrianJ submitted a new addon:

Neil Gehrels Swift Observatory - Swift and Link spacecraft, launch and on-orbit scenarios.

View attachment 49344
Neil Gehrels Swift Observatory (Swift Rescue Mission)

The Swift Observatory and Link spacecraft. Scenarios for Swift launch and Link launch and rescue mission. Alternative Kwajalein base .cfg's, "PegasusXL_DropZone" base and warning area markers file. Add-on installation, operation, data and flight notes in Doc/Swift Observatory/ folder.

For Kwajalein base options read the Doc/Swift Observatory/Swift_README.txt

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[BrianJ]

I always enjoy the PegasusXL air-launches, so I thought I'd have a go at this one
Not been much about it on the news, the last PegasusXL launching from the last(?) L1011.
Slated for take off from Kwajalein on 27 June.
Katalyst Space's "Link" spacecraft to rendezvous with Swift and give it a boost.

Not much info about the Link spacecraft other than overall mass and size.
I've given it 3 Ion engines optimistically rated at 0.1N each, its not much for orbital maneuvers.
Also given it RCS, reaction wheel control and 30kg each of Xenon and RCS propellant.
I have no idea about its robotic grappling system, so I made something very ad-hoc!
Best I could do reasonably quickly.

Its a night launch for the L1011 and PegasusXL, so theres a lot flying-by-instruments.
Quite fun

 

[Voyager_VI]

N140SC arrived in Kwajalein on the 25th.

Based on the latest HYDROPAC 1814/26, looks like launch has slipped to NET June 30.

260642Z JUN 26
HYDROPAC 1842/26.
PACIFIC OCEAN.
MARSHALL ISLANDS.
1. HAZARDOUS OPERATIONS 300730Z TO 301328Z JUN,
ALTERNATE 0730Z TO 1328Z DAILY 01 AND 02 JUL
IN AREAS BOUND BY:
A. 07-36.00N 166-16.00E, 08-07.00N 166-36.00E,
06-35.00N 169-54.00E, 06-17.00N 169-46.00E.
B. 05-15.00N 172-25.00E, 05-43.00N 172-39.00E,
05-12.00N 174-01.00E, 04-43.00N 173-49.00E.
C. 02-27.00S 178-40.00W, 03-10.00S 179-02.00W,
01-32.00S 177-21.00W, 00-50.00S 177-39.00W.
D. 04-45.00S 164-52.00W, 03-53.00S 164-29.00W,
05-27.00S 160-57.00W, 06-16.00S 161-16.00W.
2. CANCEL HYDROPAC 1814/26.
3. CANCEL THIS MSG 021428Z JUL 26.

 

[BrianJ]

Thanks! I'll see if I can make an update over the next couple of days
I haven't seen any scheduled launch webcasts - let me know if you find any.

 

[Voyager_VI]

So far, I have not had success with the capture of Swift.
I can get within about about 500 meters but after the RCS fuel is gone, I can't get any closer with the ions.

 

[Voyager_VI]

From the NASA Swift Boost Mission Page:
A mission to raise the orbit of NASA’s Neil Gehrels Swift Observatory is poised for launch no earlier than Tuesday, June 30, 6:23 a.m. EDT (10:23 p.m. UTC+12), from Kwajalein Atoll, part of the Republic of the Marshall Islands in the South Pacific Ocean.

 

[Voyager_VI]

I don't have any insider information other than having been station there and it is that time of the year and Kwajalein is on the inter-tropical convergent zone. Thunderstorms daily with the humidity. Today's snapshot

 

[BrianJ]

So far, I have not had success with the capture of Swift.
I can get within about about 500 meters but after the RCS fuel is gone, I can't get any closer with the ions.

It ain't easy. You need to keep as much RCS fuel for the docking as possible.
Doing the azimuth steering for Pegasus to align orbit is tricky, but lets say you get within 0.3deg and use the Pegasus RCS to trim the orbit to~380x420km before releasing Link.

Next thing to do is use the Ion engines to null out the remaining Rinc. (AlignPlanesMFD for this) by burning OrbNml+ when you're nearer the Descending node, and OrbNml- nearer Ascending node, til the Rinc. is ~0 .
Can take many orbits and switching OrbNml+/- .

Then check SyncOrbitsMFD, if your orbit is too large ("No Intersection") burn Ion engines Retrograde til you get an intersection. Then usual SyncOrbitMFD procedure burning Pro/Retrograde around intersection point to reduce dT.
You can use a bit of RCS to help this along.

Hopefully you have enough RCS fuel left to rendezvous. The Link doesn't have RCS Forward, so I had resort to flipping 180deg and using the RCS Back sometimes.

Well, I don't know if any of that is a help! Hope you get there

I don't have any insider information other than having been station there and it is that time of the year and Kwajalein is on the inter-tropical convergent zone. Thunder storms daily with the humidity. Today's snapshot

Possible weather issues?

I got the Swift vectors from JPL Horizons for 30 June. The "Kwajalein warning area" is pretty much the same as for 26 June so same launch azimuth - but a 10:23 UTC drop is a few minutes too early for me on my Orbiter2016 setup. I'd have to use a different azimuth, maybe 108 instead of 112 (??). Allowable within the warning area?

 

[Voyager_VI]

With the trade winds, I often wonder how many pieces actual come down in those designated warning areas, lol

 

[Voyager_VI]

0.3 degrees!, I thought I was doing good under 0.75 degrees...that 2nd stage is a bucking bronco

 

[BrianJ]

0.3 degrees!, I thought I was doing good under 0.75 degrees...that 2nd stage is a bucking bronco

Yes, the Pegasus steering is...idiosyncratic! Using Link Ion engines, you can reduce Rinc. by about 0.01deg per orbit - thats a lot of orbits to sit there flipping OrbNml+/-, but it can be done.

With the trade winds, I often wonder how many pieces actual come down in those designated warning areas, lol

I'm going with the 108deg azimuth and 10.23 UTC drop time, worry about the debris later

 

[Voyager_VI]

I think you are an hour early unless the TLE for Swift has changed a bunch, I'm seeing about 11:25-11:35 as a rabbit chase and about 1200 UTC Swift flying right over the warning box.

 

[Voyager_VI]

Using a drop time of 115400 at 12.3km and heading 112 put me right at 0.04degrees with almost all my RCS left.

 

[Voyager_VI]

Woohoo, 0.00deg alignment! Now the long slow climb uphill to catch Swift

 

[BrianJ]

Woohoo, 0.00deg alignment! Now the long slow climb uphill to catch Swift

Cool! Good luck with the SyncOrbits stuff

I think you are an hour early unless the TLE for Swift has changed a bunch, I'm seeing about 11:25-11:35 as a rabbit chase and about 1200 UTC Swift flying right over the warning box.

I use the JPL Horizons vectors. It depends how you propagate the TLE and how old it is.
The Swift LAN is drifting at about -7.6deg/day:
June 27 LAN = 105.73
June 30 LAN = 83.62
In case you want to check.
For now I'm going with the the 10:23 UTC drop for a 108 azimuth, or a couple minutes later for 112 azimuth.

 

[BrianJ]

Here's a patch .zip with a new link.msh and link.dll module that has "Forwards" RCS added (I can't be bothered with that flipping back and forth thing). Also a new L1011 take-off scenario, starts at 07:20 UTC 30 June, Swift state vectors for that time from JPL Horizons. I'll try and do a full update soon.

 

[cybro]

Have been following this one myself... There's supposed to be a Live Stream on YouTube...

We'll see how that works out... ^^^