Author Topic: Antares - Cygnus OA-5 - October 17, 2016 - DISCUSSION  (Read 83417 times)

Offline Comga

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Re: Antares - Cygnus OA-5 - October 17, 2016 - DISCUSSION
« Reply #200 on: 11/25/2016 04:42 PM »
Cygnus is still in the circular orbit at 417.7 km, 5.0 km above the ISS.

It is trailing as calculated.


When are the nanosats to be released?
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline CyndyC

Re: Antares - Cygnus OA-5 - October 17, 2016 - DISCUSSION
« Reply #201 on: 11/25/2016 09:30 PM »
When are the nanosats to be released?

In an article on the 21st, Spaceflight Now reported the first 2 would be released today at 4:05 p.m. EST (2105 GMT) and the next 2 at 7:10 p.m. EST (0010 GMT).

It would make sense if NASA limited the pre-deployment orbit raising of Cygnus to just this 5 km.

According to the NSF article on the same day, Orbital ATK & NASA ceased joint operations of Cygnus after it departed the approach ellipsoid, so it doesn't look like it will be NASA's decision, but it will be interesting to see if Orbital ATK came to the same conclusion you did. The SFN article reported the orbit would be 100km above the station. 
« Last Edit: 11/25/2016 09:37 PM by CyndyC »
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Offline sdsds

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Re: Antares - Cygnus OA-5 - October 17, 2016 - DISCUSSION
« Reply #202 on: 11/26/2016 02:39 AM »
Cygnus now reported at 502.7 x 511.2 km (semi major axis of 6877 km). 
http://www.n2yo.com/satellite/?s=41818

ISS at 408.9 km x 417.1 km (semi major axis: 6783 km).
http://www.n2yo.com/satellite/?s=25544

6877 - 6783 = 94, so that's pretty much 100 km above ISS.
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Offline Comga

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Re: Antares - Cygnus OA-5 - October 17, 2016 - DISCUSSION
« Reply #203 on: 11/26/2016 06:05 AM »
Cygnus is now reported by N2YO to be way above the ISS
Perigee: 502.6 km 
Apogee: 511.2 km
What's going on?

Cubesat deploying ;)

https://twitter.com/OrbitalATK/status/802258285650968578

Deploying that high will result in very long orbital lifetimes.
They must be planning to control and force their deorbits.
Anyone have any of those details?
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Online Olaf

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Re: Antares - Cygnus OA-5 - October 17, 2016 - DISCUSSION
« Reply #204 on: 11/26/2016 07:15 AM »
https://spire.com/insights/news/historic-maneuver-cygnus-boosts-altitude-after-iss/
Quote
The mission, which has been approved by NASA, is the first of its kind to deploy satellites into a higher orbit after departing from the ISS.
The altitude boost provided by Cygnus to approximately 500km increases the on-orbit lifespan of the Spire’s LEMUR-2 satellites from about 9 months in a typical ISS deployment to at least 2 years. That amount of time is just inside a CubeSat “goldilocks” zone where their long-term usefulness and orbital life are in near-equilibrium. 

Offline rayleighscatter

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Re: Antares - Cygnus OA-5 - October 17, 2016 - DISCUSSION
« Reply #205 on: 11/26/2016 12:39 PM »
A somewhat hypnotic view of one of the SAFFIRE samples burning.


Offline Danderman

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Re: Antares - Cygnus OA-5 - October 17, 2016 - DISCUSSION
« Reply #206 on: 11/27/2016 01:16 AM »
The requirement is to deorbit within 25 years. Since natural decay will occur from 500 km within 5 years, there is no need for a deorbit system for these satellites.

Offline Comga

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Re: Antares - Cygnus OA-5 - October 17, 2016 - DISCUSSION
« Reply #207 on: 11/27/2016 01:39 AM »
The requirement is to deorbit within 25 years. Since natural decay will occur from 500 km within 5 years, there is no need for a deorbit system for these satellites.
Do you have anything to back that up?
A simple scaling from a 9 month orbital lifetime at 400 km says that the lifetime at 500 km is right around the quarter century mark.  Much more than five years
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline sdsds

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Re: Antares - Cygnus OA-5 - October 17, 2016 - DISCUSSION
« Reply #208 on: 11/27/2016 02:23 AM »
Following the link in Olaf's post above leads to the Spire website. Spire now has the largest constellation of ship tracking satellites in the world. ISTM that gives them "expert opinion" status. They write: The altitude boost provided by Cygnus to approximately 500km increases the on-orbit lifespan of the Spire’s LEMUR-2 satellites from about 9 months in a typical ISS deployment to at least 2 years.

I bet someone at NASA even double-checked their calculations! ;-)
« Last Edit: 11/27/2016 02:23 AM by sdsds »
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