ISS & Discovery pass overhead

astrodave (David) · #1 07-08-2005, 01:13 PM

I was watching the Discovery and ISS just after seperation on NASA TV with a friend and then noticed that their orbit (20minutes later) would bring them close enough to be visible in twilight from Melbourne. We went outside and saw them both (we could fool ourselves we could just make out two dots in the binoculars). Way cool.

MiG · #2 08-08-2005, 12:16 AM

I easily saw two dots at 10x through binoculars. I doubt they were 100 m apart at the time. Some time after the pass NASA TV said they're 16 km apart.
Tomorrow I'll post one of my photos. They're on my brother's computer at the moment and he has gone to sleep.
At first I thought my brother was seeing flaws in the optics when he said he can see two dots.

Hehe, on NASA TV they're playing Barbara Streisand to the shuttle to remind the two New Yorker crew of New York.

astrodave (David) · #3 08-08-2005, 08:10 AM

I think they were still pretty close together as Discovery was still doing the ISS flyaround. A great sight wasn't it...

According to http://www.nasa.gov/returntoflight/c..._timeline.html
Saturday, August 6 (Flight Day 12):
12:24 a.m. Discovery/ISS crew farewell and hatch closure
3:22 a.m. Discovery/ISS undocking
3:52 a.m. Discovery flyaround of ISS
5:05 a.m. Final separation from ISS
9:30 a.m. Mission status briefing (flight control team video replay follows)

The Melbourne flyover occured at 4:37am Eastern USA time therefore - 45mins into the ISS flyaround and 28mins before the final burn to seperate Discovery and ISS.

MiG · #4 08-08-2005, 04:13 PM

The stated fly around separation was 400 ft (122 m). Distance from me was about 550 km (355 km ISS height and about 40 degrees elevation). Assuming they are point sources (the best case for resolving them) with 122 m separation between them, this gives an angular distance of 46 arc seconds or 0.76 arc minutes. Now the commonly stated limit for human vision is 1 arc minute and I was viewing through 10x binos (I think it was 10x, they zoom to 21x), so the two dots were separated by 7.6 arc minutes.
I'd say you are right.

I am very surprised that I could see that through binos, but the numbers make sense.