peph = CalcephBin.open('example1.dat');
AU = peph.getconstant('AU')
jd0 = 2451542
dt = 0.5
PV = peph.compute_unit(jd0, dt, NaifId.MOON, NaifId.EARTH,
Constants.UNIT_KM+Constants.UNIT_SEC+Constants.USE_NAIFID);
disp(PV)
peph.close();