Geometry and Surface Analysis

def sincpt(method: str, target: str, et: float, fixref: str, abcorr: str, obsrvr: str, dref: str, dvec: ndarray) -> Tuple[ndarray, float, ndarray, bool]:
    """
    Find surface intercept point of ray with target body.
    
    Parameters:
    - method: str, computation method ("ELLIPSOID", "DSK/UNPRIORITIZED")
    - target: str, target body name
    - et: float, ephemeris time
    - fixref: str, body-fixed reference frame
    - abcorr: str, aberration correction
    - obsrvr: str, observer body name
    - dref: str, reference frame for direction vector
    - dvec: ndarray, ray direction vector
    
    Returns:
    Tuple[ndarray, float, ndarray, bool]: (spoint, trgepc, srfvec, found)
    """

def subpnt(method: str, target: str, et: float, fixref: str, abcorr: str, obsrvr: str) -> Tuple[ndarray, float, ndarray]:
    """
    Find sub-observer point on target body.
    
    Parameters:
    - method: str, computation method
    - target: str, target body name
    - et: float, ephemeris time
    - fixref: str, body-fixed reference frame
    - abcorr: str, aberration correction
    - obsrvr: str, observer body name
    
    Returns:
    Tuple[ndarray, float, ndarray]: (spoint, trgepc, srfvec)
    """

def illum(target: str, et: float, abcorr: str, obsrvr: str, spoint: ndarray) -> Tuple[float, float, float]:
    """
    Compute illumination angles at surface point.
    
    Parameters:
    - target: str, target body name
    - et: float, ephemeris time
    - abcorr: str, aberration correction
    - obsrvr: str, observer body name
    - spoint: ndarray, surface point vector
    
    Returns:
    Tuple[float, float, float]: (phase, incdnc, emissn)
    - phase: phase angle in radians
    - incdnc: incidence angle in radians
    - emissn: emission angle in radians
    """

def illumf(method: str, target: str, ilusrc: str, et: float, fixref: str, abcorr: str, obsrvr: str, spoint: ndarray) -> Tuple[float, float, float, float, float]:
    """
    Compute illumination angles with specific illumination source.
    
    Parameters:
    - method: str, computation method
    - target: str, target body name
    - ilusrc: str, illumination source body name
    - et: float, ephemeris time
    - fixref: str, body-fixed reference frame
    - abcorr: str, aberration correction
    - obsrvr: str, observer body name
    - spoint: ndarray, surface point vector
    
    Returns:
    Tuple[float, float, float, float, float]: (trgepc, srfvec, phase, incdnc, emissn)
    """

def limbpt(method: str, target: str, et: float, fixref: str, abcorr: str, corloc: str, obsrvr: str, refvec: ndarray, rolstp: float, ncuts: int, schstp: float, soltol: float) -> Tuple[int, ndarray, ndarray, ndarray]:
    """
    Find limb points on target body.
    
    Parameters:
    - method: str, computation method
    - target: str, target body name
    - et: float, ephemeris time
    - fixref: str, body-fixed reference frame
    - abcorr: str, aberration correction
    - corloc: str, correction location
    - obsrvr: str, observer body name
    - refvec: ndarray, reference vector
    - rolstp: float, roll step size
    - ncuts: int, number of cuts
    - schstp: float, search step size
    - soltol: float, solution tolerance
    
    Returns:
    Tuple[int, ndarray, ndarray, ndarray]: (npts, points, epochs, tangts)
    """

import spiceypy as spice

spice.furnsh("metakernel.mk")

et = spice.str2et("2023-01-01T12:00:00")
spoint, trgepc, srfvec = spice.subpnt(
    "INTERCEPT/ELLIPSOID",
    "MARS",
    et,
    "IAU_MARS",
    "LT+S",
    "EARTH"
)

# Convert to lat/lon coordinates
radius, lon, lat = spice.reclat(spoint)
print(f"Sub-Earth point: lat={spice.dpr()*lat:.2f}°, lon={spice.dpr()*lon:.2f}°")

spice.kclear()