More from @planet4589

Jonathan McDowell

@planet4589

4 Jul

OK I found a much better solution for the Starship flight. I was starting it off with SECO at much too high an altitude.
Better solution: about 50 x 250 km

The GoogleEarth path doesn't look dramatically different, the ground track is pretty much identical

This solution satisfies the 250 km max altitude, low perigee, and Hawaii range. I'm much happier now!

Read 5 tweets

Jonathan McDowell

@planet4589

4 Jul

I took a look at what's know for the proposed marginal-orbit trajectory for the Starship/Super Heavy test flight. I came up with an OK fit with an orbit that is about 70 x 860 km x 26.4 deg. The relatively high apogee is needed to accomodate a low perigee and the range to HI

Here's some plots of the assumed trajectory superimposed on GoogleEarth:

And here is my fake TLE:

Read 4 tweets

Jonathan McDowell

@planet4589

3 Jul

China's SAST launched a Chang Zheng 2D from Taiyuan at 0251 UTC carrying 5 sats: 吉林一号宽幅01B (Jilin-1 Kuanfu 01B), 吉林一号高分03D卫星 01,02,03 (Jilin-1 Gaofen 03D Sats 1,2, and 3) and 星时代-10卫星 (Xingshidai-10)

The Jilin-1 series of commercial Earth imaging satellites is operated by the Changguang Sat Tech Ltd in Changchun, Jilin province. The Jilin-1 Kuanfu (wide) series has a large field of view while the Jilin-1 Gaofen (hi-res) series has narrow hi-res imagers.

Xingshidai-10 is a small imaging satellite from Guoxing Yuhang Keji YG in Chengdu (the company markets itself in English as ADA Space).

Read 4 tweets

Jonathan McDowell

@planet4589

2 Jul

The mystery 'BD-28' commercial satellite deployed from J-SSOD-13 on ISS on Jun 22 is actually G-SATELLITE 2. The satellite is owned by OneTeam, a collaboration of Tokyo U's Nakasuka Funase Lab and various companies.

G-SATELLITE 1 was deployed in similar secrecy in Apr 2020. The satellite's mission was advertising, to promote the Tokyo Olympics.

It contained mechamisms to deploy to the exterior (but remaining attached)
a display with figurines of robot characters from the 'Mobile Suit Gundam'
anime television series, and a camera to image them against the Earth in the background

Read 5 tweets

Jonathan McDowell

@planet4589

17 Jun

@abigailStev

I thought I'd give my own spin on Abbie's black hole tweet (although you should read her own discussion of it and follow her at @abigailStev ) ....

@abigailStev

@abigailStev What is 4U 1543-47? It's a 'high mass X-ray
binary', a binary star with an A-type main sequence star called IL Lupi, about twice as massive as the Sun, tightly orbiting a black hole 9 times the mass of the Sun.

@abigailStev

@abigailStev The two objects are so close to each other that matter from the
A star is being torn off and collects in a disk
around the black hole, slowly trickling in.

Read 13 tweets