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33 votes

Why are there four RTGs in a row sitting in this room? What are they waiting for? Were they built together and stored for separate launches?

There were seven General Purpose Heat Source - Radioisotope Thermal Generators (GPHS-RTGs) assembled (there were parts for an eighth). The seven would eventually fly in space on four different ...
Organic Marble's user avatar
28 votes
Accepted

Why do we use Chebyshev polynomials to predict positions of solar system bodies?

I'm also surprised that JPL uses a numerical model rather than doing a n-body physics simulation of the Solar System. JPL does use an n-body physics simulation of the solar system. It's a very ...
David Hammen's user avatar
  • 74.8k
18 votes

How are the "lucky JPL peanuts" shared post-pandemic?

People received individual packages of peanuts and could sneak one under their mask. This page shows people holding individual packages of peanuts. And this video explains the procedure briefly.
Wyck's user avatar
  • 1,584
16 votes
Accepted

What is the numbering system used for the DSN dishes?

I found a sort of explanation in "Uplink-Downlink" the NASA history of the DSN. The first digit [range of digits, really, see the table] gives the geographical area. The second digit gives the ...
Organic Marble's user avatar
12 votes

What is the numbering system used for the DSN dishes?

Looking at the history of DSN on Wikipedia, it appears that the tens-place digit originally was allocated to identify the region or site, and within a region/site the dishes were numbered sequentially ...
Russell Borogove's user avatar
10 votes
Accepted

Why did Curiosity perform TCMs?

We try, but our ability to model reality isn't perfect. In fact, we don't even know the gravitational constant $G$ to more than 4 significant digits. Our data on the masses of the sun and the planets ...
Christopher James Huff's user avatar
10 votes
Accepted

What is the history behind having peanuts in mission control during critical missions?

It turns out this goes way back to the 1960s. Landing on a celestial body isn't easy; JPL had suffered a series of failures during the Ranger missions, some during launch and others further on in each ...
HDE 226868's user avatar
  • 3,227
7 votes
Accepted

What did JPL's 1939 lunar lander look like and what practical aspects of landing on the Moon did this engineering design address?

The Jet Propulsion Laboratory didn't exist under the JPL name until 1943-1944. What existed in 1938-1939 was its predecessor, rocketry experiments at the Guggenheim Aeronautical Laboratory at the ...
David Moews's user avatar
7 votes
Accepted

When NASA spacecraft arrive at Mars, is Mars always always above the horizon in the US?

Easy enough to verify by computing the Alt/Az of Mars on the descent date/time of NASA spacecraft. I picked a few, got the descent times from Wikipedia, and generated the Alt from Cape Canaveral ...
Greg Miller's user avatar
6 votes
Accepted

What are those plastic hoses on Perseverance used for?

The original poster on reddit seems to have come to a conclusion to their question only a couple of days after posting it, and I've not found anything that seems to contradict their conclusions. Here'...
Starfish Prime's user avatar
6 votes
Accepted

What time zone is used for JPL tests?

UTC This page gives launch local time as Friday, September 7, at 9:30 a.m in Virginia, USA. Virginia is Eastern Time (GMT-5) and September is in Daylight Savings Time which accounts for the ...
Organic Marble's user avatar
6 votes

Does NASA's Deep Space Network sometimes listen to other space agencies' spacecraft "just for the heck of it" or other non-mission related reasons?

China has done it with NASA China used signals sent from NASA’s Juno probe orbiting Jupiter to test the capabilities of ground stations vital to its deep space ambitions. Scientists involved in ...
Fred's user avatar
  • 13.1k
6 votes

Access to Chebyshev coefficients from JPL ephemerides

Your question is slightly ambiguous, a file containing the Chebyshev coefficients wouldn't be an ephemeris, but it's something you could use to generate an ephemeris. Regardless, the article Format ...
Greg Miller's user avatar
5 votes

What will the US government start to label its GPS spacecraft after SVN 99

The numbering of 01-99 you refer to is the one used for the PRN of the satellites. The SVN is numbered using 3 digits in IGS files and is therefore not going to run out anytime soon. PRN's are often ...
Alexander Vandenberghe's user avatar
5 votes

How to obtain Chebyshev coefficients directly from the JPL Horizon's interface?

The best and most concise answer is here The "gold standard" is the SPICE toolkit. You can read more about using spice in this excellent answer. The JPL Development Ephemerides are lists of the ...
uhoh's user avatar
  • 149k
4 votes
Accepted

When was the idea behind the DESCANSO Book Series first conceived, by whom, and what is its "mission"?

From the foreword of Volume 1: The Deep Space Communications and Navigation Systems Center of Excellence (DESCANSO) was recently established for the National Aeronautics and Space Administration (...
Hobbes's user avatar
  • 128k
4 votes

Why are JPL using this expression to emulate Schwarzschild orbits?

To understand the meaning of the formula, one needs to face its origins in general relativity. GR is not just about corrections to Newtonian expressions for gravitational forces and accelerations. It ...
nanoman's user avatar
  • 454
4 votes
Accepted

What information was stolen from JPL during the Raspberry Pi hack?

As an information security professional this makes me cringe, but I'm not in the last surprised. I've read the OIG report, there's not that much information on the data that is lost, but the report ...
GdD's user avatar
  • 20.3k
4 votes
Accepted

Tradeoffs between using two 34 m and one 70 m Deep Space Network dish?

The major downside to using a pair of 34-meter antennas is that they have only half the collecting area of a single 70-meter antenna, and produce only half the signal strength. Beyond that, on the ...
Mark's user avatar
  • 15.3k
4 votes
Accepted

Are the Perseverance rover's "drivers" working on Martian sols or Earth days right now?

A team of about 350 scientists and engineers are keeping "Mars time" right now ! From Business Insider's article "Now on 'Mars time,' NASA's Perseverance team shifts their work hours 40 ...
Cornelis's user avatar
  • 7,545
4 votes

Access to Chebyshev coefficients from JPL ephemerides

The best method I've found is to use Brandon Rhodes' Python "jplephem" from here, specifically using the _load() function of an SPK segment. You get a ...
ChrisR's user avatar
  • 6,220
3 votes

Why did Curiosity perform TCMs?

The first trajectory course maneuver, and oftentimes, the first two TCMs, are absolutely essential given NASA's planetary protection protocols. Trajectories toward Mars are designed so that there is ...
David Hammen's user avatar
  • 74.8k
3 votes

Access to Chebyshev coefficients from JPL ephemerides

Update : I have found a way to extract Chebyshev coefficients at a requested date for a particular body using CSPICE. Here the program that allows to do this : ...
GuillaumeJ's user avatar
2 votes

How to obtain Chebyshev coefficients directly from the JPL Horizon's interface?

You don't get those from HORIZONS. You download them from here. They are best accessed with the SPICE toolkit, or you can roll your own to extract the Чебышёв coefficients from the SPK files.
Mark Adler's user avatar
  • 58.2k
2 votes

Lunar landing module and orbiting space craft personnel transfer

While the modules were launched with the engine in between, the modules docked nose-to-nose. The crew moved between the modules using hatches in the noses of each module. Image location Related ...
Organic Marble's user avatar
1 vote
Accepted

Was the famous SPICE package of programs, utilities and data kernels named after "Melange" found on the planet Arrakis?

According to this, SPICE stands for Spacecraft ephemeris Planet (plus moon, comet, asteroid) ephemerides Instruments (geometric information such as field-of-view, shape, orientation) C-matrix (...
Bob Werner's user avatar
  • 1,124

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