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Last revised on 2002 DEC 13 by E. D. Wright.
STATES is a cookbook program that demonstrates how to use Toolkit
routines to obtain state vectors.
The STATES `cookbook' program illustrates the use of SPICE SPK files and
CSPICE subroutines. The program performs look-ups of state vectors from
an SPK file.
STATES demonstrates the use of the following high-level subroutines:
To run STATES, you need a binary SPK ephemeris file and knowledge of the bodies and corresponding time intervals contained in that file. The utility program named BRIEF summarizes a binary SPK file; NAIF IDs Required Reading lists body names and codes. In addition to an SPK file, you also require access to a leapseconds kernel (LSK).
Below, find an example STATES session that calculates the state of the Moon relative to the Earth at various times during the first day of January, 1990.
STATES prompts you for the integer codes or string names of target and observer bodies, a reference frame for the state evaluation, the aberration correction to use with the evaluation, the end-points (expressed in UTC) of a time interval, and the number of evaluations (state look-ups) to perform over the assigned time interval. Given this input, STATES displays to the terminal the state, (position and velocity) at each evaluation of the target body as seen from the observer in the declared reference frame adjusted for the specified aberration correction.
Please note: FORTRAN and C versions of the program can output numerical values in slightly different formats.
It is assumed the kernel files used by STATES exist in the current directory (i.e. the directory from which your execute STATES). This particular session was run on an Intel box using the LINUX operating system.
First, create the binary SPK kernel "cook_01.bsp" by running the CSPICE Toolkit TOBIN application on the transfer format file "cook_01.tsp" located in the CSPICE data directory. The program also requires a leapseconds kernel to run; an example leapseconds kernel, 'cook_01.tls' exists within the same directory. Now, execute STATES:
Welcome to STATES
This program demonstrates the use of NAIF S- and P-
Kernel (SPK) files and subroutines by computing the
state of a target body as seen from an observing
body at a number of epochs within a given time
interval.
Enter the name of a leapseconds kernel file: cook_01.tls
Enter the name of a binary SPK ephemeris file: cook_01.bsp
Enter the name of the observing body: earth
Enter the name of a target body: moon
Enter the number of states to be calculated: 5
Enter the beginning UTC time: 1 jan 1990
Enter the ending UTC time: 2 jan 1990
Enter the inertial reference frame (eg:J2000): j2000
Type of correction Type of state
-------------------------------------------------------------
'LT+S' Light-time and stellar aberration Apparent state
'LT' Light-time only True state
'NONE' No correction Geometric state
Enter LT+S, LT, or NONE: LT+S
Working ... Please wait
For time 1 of 5, the state of:
Body : moon
Relative to body: earth
In Frame : j2000
At UTC time : 1990 JAN 01 00:00:00
Position (km) Velocity (km/s)
----------------------- -----------------------
X: 3.1817356914228073e+05 5.3394535681481514e-01
Y: -1.9411657590890554e+05 7.7051535844816144e-01
Z: -7.7812550159748964e+04 4.3386380567914284e-01
MAGNITUDE: 3.8074986290962604e+05 1.0329711339369498e+00
Continue? (Enter Y or N): Y
For time 2 of 5, the state of:
Body : moon
Relative to body: earth
In Frame : j2000
At UTC time : 1990 JAN 01 06:00:00
Position (km) Velocity (km/s)
----------------------- -----------------------
X: 3.2915688826278772e+05 4.8249639220368934e-01
Y: -1.7715581503624297e+05 7.9947042534779911e-01
Z: -6.8315337774688582e+04 4.4523496484754310e-01
MAGNITUDE: 3.7999398056714883e+05 1.0344998324882222e+00
Continue? (Enter Y or N): Y
For time 3 of 5, the state of:
Body : moon
Relative to body: earth
In Frame : j2000
At UTC time : 1990 JAN 01 12:00:00
Position (km) Velocity (km/s)
----------------------- -----------------------
X: 3.3900715098782443e+05 4.2906743233110589e-01
Y: -1.5959674510107530e+05 8.2587395364385063e-01
Z: -5.8588018067307996e+04 4.5515161940699311e-01
MAGNITUDE: 3.7924863259976875e+05 1.0360162380210756e+00
Continue? (Enter Y or N): Y
For time 4 of 5, the state of:
Body : moon
Relative to body: earth
In Frame : j2000
At UTC time : 1990 JAN 01 18:00:00
Position (km) Velocity (km/s)
----------------------- -----------------------
X: 3.4768335621335648e+05 3.7382616249951184e-01
Y: -1.4149583716010855e+05 8.4960221441502703e-01
Z: -4.8662586928824239e+04 4.6356151096043718e-01
MAGNITUDE: 3.7851398321334057e+05 1.0375255162895767e+00
Continue? (Enter Y or N): Y
For time 5 of 5, the state of:
Body : moon
Relative to body: earth
In Frame : j2000
At UTC time : 1990 JAN 02 00:00:00
Position (km) Velocity (km/s)
----------------------- -----------------------
X: 3.5514823394910217e+05 3.1695019646037181e-01
Y: -1.2291215332598702e+05 8.7053938526942165e-01
Z: -3.8572119287635753e+04 4.7041716136973366e-01
MAGNITUDE: 3.7779025119599997e+05 1.0390325086601906e+00