# Tag Info

18

tl;dr: at an apparent magnitude of about +18.5 you need a several meter telescope and a dark sky. Hubble can do it too. So by reflected sunlight, definitely not by eye. The exhaust from a Methalox (CH4 + LOX) engine barely makes any light in the visible, so no help there. Starting with the math from this answer: I'm going to characterize the 55 x 9 meter ...

15

If you want an easy way to think about it, imagine how bright it might be in low Earth orbit, 240 miles up (which is just a bit lower than the International Space Station). However bright that is, it will be only a millionth as bright when it’s near the Moon, 240,000 miles away (and so a thousand times the distance). Is it likely that it will be bright ...

15

Looks like it was indeed Goddard. Key search term was 'flash powder' not gunpowder. The Smithsonian has a box built and used by American rocket pioneer Robert H. Goddard in experiments in 1916 to determine the amount of magnesium flash powder to be carried in a unmanned rocket to strike the surface of the Moon to signal its arrival. Source: https://...

14

Yes, the Starlink satellites were visible from earth with your naked eye and have been seen and recorded by several people. See also https://vimeo.com/338361997 and read about it here. Gizmodo: Breathtaking View of SpaceX Starlink Satellite ‘Train’ Triggers Wave of UFO Sightings

14

In general satellites are not "painted". They are covered in a variety of Multi-Layer Insulation (MLI) blankets with varying optical qualities. I have seen MLI in silver, black, and gold - sometimes on the same spacecraft. In addition, spacecraft often have radiators (most usually silver) and sometimes even louvers that cover radiators. A spacecraft is ...

14

Typically, kerosene-LOX engines run fuel-rich, with an oxidizer:fuel mass ratio of about 2.5:1 (as compared to 3.5:1 for complete combustion), leaving significant amounts of unburned carbon soot in the exhaust, which glows yellow as it combusts with oxygen in the atmosphere. The oxidizer:fuel mass ratio for complete combustion of kerosene with hydrogen ...

11

No, the reflector hasn't been deployed. Project head, Alexander Shayenko reported about it (RUS) (ENG) today. Early report information On July 17th the team reported about possible success (RUS) (ENG). They analyzed the TLE of orbits of 73 satellites in cluster. Based on braking factor(#9 element) and ballistic ratio(#11 element) they found 2017-042F, ...

9

Yes, it happened at least on 13th April 2020 at 21:25:02 UTC: https://sattrackcam.blogspot.com/2020/04/starlink-train-photographed-from.html The image above (image ISS062-E-148365, original at high resolution here) was shot from the International Space Station (ISS) on 13 April 2020, 21:25:02 UT. It shows the Aurora Australis (southern lights) and a train ...

9

I think Wikipedia's Bristol Siddeley Gamma; Advantages of kerosene / peroxide engines can shed some light on the missing light. The combustion formula of kerosene and hydrogen peroxide is $$\mathrm{CH_2+3H_2O_2}\to\mathrm{CO_2+4H_2O},$$ and you can see that the exhaust is mostly water, which results in a clean, transparent flame and increases thrust ...

8

Well, since I used to work for 'em (L3), I'll omit the argument about whether is this on-topic: HALO stands for High Altitude Observatory. It's an airplane (several airplanes) The existing contract requires L3 to maintain and operate a fleet of specialized Government-owned Gulfstream II-B (G-IIB) aircraft – HALO I, II, and IV – which are sensor-equipped to ...

6

Per the official NASA history of Vanguard it was for visibility and thermal control. (Bolding mine) Tousey had made some of the first calculations in the fall of 1955, contributing his knowledge of optics to ensure that protective coatings on the exterior of the booster and on the satellite shell would have ...

6

Here's a map that shows the general visibility for Antares launches (that was the rocket the weatherman was talking about, although it won't be flying again until 2016): I once watched a Minotaur V launch from Wallops down on Brighton Beach in New York. It was clearly visible. It was also a night launch, it probably wouldn't have been visible during daytime....

6

As an answer to the question in your title, NASA photographer Joel Kowsky captured this stunning composite earlier today in Banner, Wyoming. The positioning required to perfectly frame Station during this solar transit took months of planning, and the window of opportunity was brief enough that it was shot at 1,500 frames per second with a high-speed camera. ...

6

From what I can tell, you're right -- every article I've read on the topic cites Escobal, because they all feel they have to acknowledge the existence of an analytical solution, but then they all describe their favorite numerical method, and give tables of its performance on various sets of simulated data, but none of them seem to actually compare their ...

6

The object will hit the Moon on the far side, not visible from Earth (emphasis added): There have been a few folks who, for one reason or another, have asked me not to post their data. This includes some data before the object made a close lunar flyby on 2022 January 5; those data are quite important in lowering the uncertainties. With all the data, we've ...

5

To be stationary above ground we need an orbit with a period of about 24 hours ( exactly 23 hours, 56 minutes and 4 seconds, one sideral day). Such an orbit is called GEO and is 35,786 km above ground). Many communication and TV satellites are placed into a GEO orbit. We have rockets for the transfer of astronauts to the ISS into a LEO orbit. But we don't ...

5

The different brightness is caused by the fuel. The liquid fuel rockets burn hydrogen with oxygen, both are gases and the reaction product is hot water vapour, also a gas. But pure gas flames emit very little light, that is why gas mantles are used for camping gas lanterns. The hot solid mesh emits far more light than the hot gas heating the mesh. The ...

5

Some breaking news on this, according to this source (not the most reputable, to be sure) the reflectors have failed to deploy. They link to this source which appears to be from the creators of Mayak, saying that technical failures have occurred and they are still trying to diagnose them. I don't speak Russian and Google Translate only makes it partially ...

5

Yes, Humanity Star was spotted at "0106 on [January] the 27th New Zealand time (1206 on the 26th UTC.)" The sighting was made from Pukehina, Bay of Plenty, New Zealand. It was observed again on February 25th at 9:29 NZT, and it definitely looks very "disco-flashy" on the video, in my opinion.

5

Much of the Unity spacecraft appears (almost) transparent in this image; you can see the blue sky right through it. This is absolute nonsense; you cannot see the sky through Unity's airframe. It is opaque. The upper surface of Unity is indeed painted mainly white. The underside appears to be painted in a dark blue and black iris-and-pupil design, providing ...

5

A very back-of-the-napkin calculation, appropriating the calculations from here: Assuming the JWST is in fact a 17m sphere (actual 21 x 14), with perfect reflectivity (as pointed out in the comments this is generally not the case), the absolute magnitude is: $$M_{Abs} = 5 \left(\log_{10}(1329) -\frac{1}{2}\log_{10}(\text{1}) -\log_{10}(0.017)\right) = 24.5$$ ...

4

Rocket engines burning in vacuum produce large exhaust plumes that rapidly spread outward to 'fill' the vacuum. This means that for a distance of many dozens of meters - or more - they produce a visible cloud of gas that can catch sunlight and produce very large, visible artifacts in a clear night sky. So - engine burns near Earth (departure, or arrivals ...

4

tl:dr: ...neither telescope could begin to resolve the other when on opposite sides of the orbit, but only by a factor of ten. So the question really boils down to one of orbital mechanics, mission design, and perhaps telecommunications because they probably would always want to avoid the two telescopes fitting into the same ground station dish antenna's ...

4

The Baker Nunn camera used a very special film format, ten inches of 55 mm wide cinemascope film, (254 mm by about 46 mm.) From http://bollerandchivens.com/?p=561 So photographic plates or sheets of instant film could not be used, only flexible film on a roll. The Baker-Nunn Satellite Tracking Stations like those at Hawaii were equipped with a darkroom, so ...

3

As seen in the photos below from https://terra.nasa.gov/about Terra is reddish, so the answer to Why is Terra reddish? is exactly what you have suspected; because it is wrapped in a thermal protection film that is reddish in color. However, the answer to a more interesting question: Why am I surprised that Terra appears reddish? would have several ...

3

I think it is a retroreflective material like that used for High-visibility_clothing. There are reflective tape originally developed by 3M. A reflective coating of tiny glas spheres is used as retroreflectors. The surface should reflect radiation (usually light) back to its source with minimum scattering. Using retroreflectors in space has a long tradition. ...

3

There is an issue with geosync orbit: You are in the outer Van Allen radiation belt. Oodles of relativistic electrons running around. Your space craft has to be shielded against those. If you parked at geosync orbit, then you'd receive about 25 Sieverts of radiation per year -- about 5 times lethal dose. Even that requries a 3 mm protective shell. Solar ...

3

Yes, if you have a telescope or really good set of binoculars. The article you linked even states this: “It’s not going to be visible to the naked eye, but really any amateur astronomer with a half decent telescope should be able to do it,” the professor said. “Or a big lens on a regular camera like a telephonic lens, they should be able to pick it up and ...

3

The ellipsoidal stuff can be fun, but in the end the problem is that the Earth isn't really ellipsoidal either, so pretending it is doesn't get you much beyond pretending it is a sphere. For efficient calculation of very good approximate answers on an ellipsoid, you'll want to take a look at geographiclib, the motivation and capabilities of which are ...

2

The notable amateur astronomer, award winning IOTA member and expert asteroid occultation timing-ist Derek C. Breit wrote on the Seesat-l (visual satellite observing) mail list that his video shows the second stage/Roadster before the start of the escape burn. See his post here. Source He links there to the video can be found at bottom right in ...

Only top voted, non community-wiki answers of a minimum length are eligible