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Questions tagged [spice]

The SPICE is a information system released by the Navigation and Ancillary Information Facility (NAIF) to assist scientists and engineers. The system includes data sets called "kernels" and the SPICE Toolkit, a software library needed to read the kernel files and to calculate observation geometry parameters of interest to scientists and engineers.

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172 views

What does w.r.t. mean? I've found it in the summary of jup365.bsp [closed]

Inside summary of the file jup365.bsp I have found this: ...
13 votes
1 answer
392 views

Different Earth-centered ICRF positions in GMAT and Skyfield/Spiceypy with DE421

I compared the Earth-centered positions from the Moon in the ICRF (i.e., in GCRF) using three different sources: SpiceyPy (https://pypi.org/project/spiceypy/) Skyfield (https://rhodesmill.org/...
1 vote
0 answers
75 views

Obtain all the points of the orbit of a celestial body in the solar system

How can I render (or plot) the orbit of a planet using SPICE? Sorry, I'm not English and I don't know how to say to draw the path that the planet follows around the Sun (their orbit or, maybe, ...
4 votes
1 answer
230 views

Computing viewing geometry of Solar System targets from ground-based observatories using SPICE kernels

SOLVED. I want to calculate the visible part of an asteroid (I'll use the Moon in this example) from the Chile VLT observatory (latitude, longitude coordinates = -24.62733, -70.40417). On the NAIF ...
3 votes
1 answer
249 views

Which SPICE kernels I have to load to calculate state vector of the outer planets

I'm developing a software to show the planets in the sky. I have loaded the following kernels: ...
2 votes
0 answers
97 views

Beginner to simulating communications systems of space missions. I have GMAT, MATLAB and NASA's SPICE library. Where would I start?

I recently managed to load SPICE kernels into GMAT to simulate the trajectories of real missions, and got its MATLAB interface working (still trying to understand how to use the two software together)....
1 vote
0 answers
71 views

How to compute light time correction for eclipse entry/exit timings?

I used a typical geosynchronous orbital parameters and generated lunar shadow penumbra entry and exit timings using OREKIT and GMAT. GMAT has an option to include light-time correction (also for ...
3 votes
1 answer
295 views

Horizons ephemeris - how did they calculate that “Keplerian GM” value?

I’ve been playing with the NAIF’s SPICE library for some time (CSPICE in particular). In order to obtain the state vector of an asteroid from its osculating elements, I’m calling the “conics_c” ...
3 votes
1 answer
119 views

Why does Earth's North Pole RA flip by ~180 deg around AD2000 relative to SSB? (JPL Horizons data)

Using JPL's Horizons API I see that the Earth's North Pole RA flipped by ~180 degrees quite suddenly around AD 2000. It was pretty stable around 180deg for at least 1000 years prior, and then remains ...
0 votes
0 answers
282 views

SPICE C compiling issues

I have been trying to run Spice in C code for one week but I have not succeeded. I know how to use Spice in Matlab and Python but I need to use it in C this time. I have followed this tutorial by JPL....
4 votes
0 answers
64 views

Where to get data for axis of rotation of solar system bodies?

Where can I get data for the axis of rotation of the (major) bodies of the solar system? For each solar system body, I want to get a unit vector of its axis of rotation (at a specified point in time). ...
1 vote
0 answers
231 views

Osculating conic orbital elements: Comparing SPICE's oscelt to MATLAB's ijk2keplerian functions

I have been using the SPICE Toolbox and wanted to derive orbital elements from a state vector $X$ in ECEF coordinates [1] in order to define a circular orbit around Earth. To do so I need first ...
6 votes
4 answers
910 views

Access to Chebyshev coefficients from JPL ephemerides

I want to generate an ephemeris file containing the Chebyshev coefficients, similar to how we can generate ephemeris file of positions with Horizon tool (https://ssd.jpl.nasa.gov/horizons/app.html#/). ...
1 vote
1 answer
90 views

Change frame center definition of Chebyshev coefficients

I am using SPICE to read and store Chebyshev coefficients to then compute position of Solar System bodies in my navigation software (see this post). The coefficients are defined with respect to the ...
1 vote
2 answers
147 views

TT-TDB with SPICE from ephemerides kernels as 'de440t.bsp'

I am a new SPICE user. I would like to ask a question: does anyone know if it is possible with some SPICE function to get the TT-TDB value directly from kernels as 'de440t.bsp', body id '1000000001'?
4 votes
1 answer
283 views

How to get MARS2020/Perseverance EDL trajectory data from spice kernels?

For MSL EDL it is available this answer: How to retrieve MSL EDL trajectory using Javascript and webgeocalc API? How can I adapt it to MARS2020/Perseverance?
4 votes
2 answers
183 views

SPICE toolkit occultation finder doesn't work with spacecraft

I've to know if the sun is occulted by earth from my spacecraft which is in low earth orbit with these parameters (a:6700 km, e:0.0, i:5°, ...). I run the following method with search window start at ...
2 votes
0 answers
324 views

Lunar eclipses using SPICE toolkit, missing ephemeris data

I want to figure out lunar eclipses as seen from a point on the Moon using SPICE. To generate ephemeris for the point on the Moon, I use the code provided in this answer. Instead of ...
3 votes
0 answers
152 views

determining lunar eclipse with SPICE toolkit

Is there any way to determine if the Sun is visible from the Moon at a given latitude/longitude and at a given instant in SPICE toolkit? Specifically, determine if there is lunar eclipse or transit ...
3 votes
1 answer
503 views

SPICE defining a topocentric frame on the Moon

I would like to define a topocentric frame for a particular spot on the moon. From the frames required reading i have this: ...
3 votes
1 answer
73 views

Does SPICE function gftfov account for occultations?

I need to determine when an antenna on a spacecraft can see a ground station on Earth at particular epochs. I have generated all the necessary SPICE kernels necessary as well as using the NASA ...
2 votes
1 answer
160 views

How to retrieve MSL EDL trajectory using Javascript and webgeocalc API?

I found a "javascript gateway" to NASA SPICE data, the "webgeocalc" web api: https://wgc2.jpl.nasa.gov:8443/webgeocalc/example/perform-calculation.html It works both online and ...
6 votes
2 answers
1k views

How to convert a SPICE SPK kernel into human-readable data using SPICE toolkit and utilities

SPK2OEM is one of many of SPICE tools available here: https://naif.jpl.nasa.gov/naif/utilities_PC_Windows_32bit.html I am trying to extract ephemeris from one of the SPK files listed here: https://...
1 vote
1 answer
265 views

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

This question is NOT about a fictional planet: This question is about NASA JPL history and the naming of SPICE. It is not primarily about the fictional planet Arrakis nor the fictional drug Melange ...
3 votes
0 answers
122 views

How to get MSL coordinates during EDL from SPICE kernel?

Upon trying to extract MSL position above surface by decoding a SPICE kernel, I am gettin this error: At epoch 3.9750216818313E+08 TDB (2012 AUG 06 05:16:08.183 TDB), there is insufficient ...
3 votes
1 answer
279 views

Should coordinate transformations from J2000 to ITRF93 in quaternions be cyclic?

I used SPICE's pxform at an interval of epochs to determine the transformation from J2000 (inertial) to ITRF93 (Earth body-fixed) frame. Then, I converted these rotation matrices to quaternions with ...
4 votes
1 answer
180 views

How can I generate Chebyshev cofficients from SPICE for J2000 Inertial to Moon ME Frame?

I want to extract the Chebyshev coefficients in order to be able to calculate the time-varying transformation from the ICRF / J2000 Inertial frame to the Moon ME (moon mean earth) frame. I know I can ...
2 votes
1 answer
410 views

Rotation matrix from J2000 to ITRF2008

I want to rotate a vector from the inertial J2000 frame into ITRF2008. I am using the NASA SPICE library, which provides a rotation matrix from J2000 to ITRF93 (they plan to upgrade the library to a ...
4 votes
2 answers
746 views

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

I'm from Spain and I'm currently finishing my degree in Aerospace Engineering. I am starting with all of this. My objective is to obtain the Chebyshev coefficients for the major planets position, ...
2 votes
0 answers
131 views

Suggestion for software which allows orbit data generation under different conditions (such as J2, ATM drag etc)

I am an amateur astrophysics enthusiast trying to generate orbit data. What I want to achieve: I want to be able to generate orbits while only considering effects of (J2, J3, atm drag, solar ...
4 votes
0 answers
175 views

SPICE GFPOSC is returning incorrect sunrise (and sunset) times for topocentric frames

I cannot get SPICE to produce accurate sunrise times for topocentric frames I specify. I'm using spiceypy to interface with SPICE. As a first test, I set up topo coordinates for the MARE landing site,...
3 votes
1 answer
304 views

How does one use SPICE to compute the Greenwich sidereal time as an angle?

I'm looking at the BMW book† and see that equation 7.5-7 gives $\alpha_0 = \theta = \theta_g + \lambda_E$ as the equation for right ascension (for some launch site at east longitude $\lambda_E$). $\...
1 vote
0 answers
434 views

How to define a body-centered ICRF/J2000 frame in SPICE?

I am trying to define a reference frame in SPICE that is Centered on a particular body, for example Mars, and with axes parallel to J2000/ICRF After going through the required reading for reference ...