# Tag Info

25

How? Simple, because they launched into those orbits. Why? Well, first, let me explain what their orbits actually are. IRAS (13777) and GGSE-4 (2828) are both in high-inclination orbits, 70° and 99°, respectively. The latter is slightly retrograde, as is common for sun-synchronous orbits. However, to fully understand in what plane they are orbiting, we ...

7

It turns out it might be very common for astronauts on the ISS (or previously the MIR) to spot satellites. This is the distribution of the number of satellites in LEO for different altitudes As you can see the ISS, with its $\sim 400 \; km$ altitude, is quite safe and alone below the huge carcass of LEO satellites moving around $800 \; km$ (it is also true ...

5

I used this solar system simulation to look for planet positions in an arc, more or less as shown in this image of the Grand Tour (provided by @userLTK). When I entered Voyager 1's launch date in the simulation, I got this image: Jupiter-Saturn-Uranus are spread around 135 degrees, Jupiter-Saturn-Neptune are spread around 180 degrees. I basically checked ...

4

Propagating $N$ objects and checking $N(N-1)/2$ distances at each small time step is indeed computationally inefficient to the point of being impractical. If I recall correctly, there are currently ~17000 catalogued objects on SPACE-TRAK. Assuming to check for collisions every second,* we would have to compute $10^{13}$ Euclidean norms in a single day. Some ...

4

That is called the synodic period.

3

For deep space missions, there usually is a conjugation analysis, but not for the reasons you predicted. In fact, they do it to see if there's any secondary objects that can be studied while on the way to their destination. The majority of asteroids that have been photographed up close, in fact, were such accidents. From the Wikipedia Article, here's a few ...

3

Looking at STK and the public elements for each object. Unfortunately I can't do a conjunction report, as I can't seem to get JUNO into STK unfortunately... But here's a few photos: Juno Flyby: ISS/Tiangong at the time of closest approach: Given this, hands down the answer is Tiangong. I don't have an exact distance for you, but it will be within 4 track ...

3

MSR is one of LeoLab's radar stations (LeoLabs being the people who tweeted about the potential collision, a company whose busines is monitoring satellites). It lives in Midland, Texas, and as such is called the Midland Space Radar. I'm not sure what the contours show, but they're presumably related to the region that the radar can observe.

2

It looks like you're working from the JSpOC Spaceflight Safety Handbook for Operators (https://www.space-track.org/documents/JSpOC_Spaceflight_Safety_Handbook_For_Operators.pdf). In this case they define the RIC frame as identical to what is often called the UVW frame (https://www.space-track.org/documents/JSpOC_Pc_4Aug16.pdf pg 3). This frame is defined ...

2

Astrowatch has the answer, which is: Per Flight Rule B4-101, a “late conjunction” call results in the crew being ordered to close the hatches between Station modules and enter the Soyuz vehicles – which serve as lifeboats during their docked stay at the ISS – before TCA (Time of Closest Approach) breaches the 10 minute mark. It is my understanding that ...

2

There's a disadvantage to placing satellites too close together for no reason, if struck by a micrometeoroid pieces of both the space debris and satellite pose a danger to its companion; it's essentially doubling the chance of a strike. Here's what happens when a bullet strikes a sheet of glass: The answer you linked to for "How closely spaced are ...

2

How About Half a Kilometer The GRACE mission was mentioned in a very complete answer by @Rob (mentioned as GRACE-FO, which is the current mission replacing GRACE). However, unmentioned is the fact that the satellites swapped positions periodically. Since the satellites use K-band (and laser for GFO) ranging, the rear satellite was exposing its K-band "...

1

If the intention is to get really close, rendezvous is possible. Though is common to just take them up together. I.e: LISA pathfinder has 3 separate bodies that have been held close for prolonged periods of time. Also: docking is a thing as is landing on asteroids, so if we want to get close, we can. Otherwise there is really no need to have satellites ...

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