The relevant geometric parameters (e.g. latitude, longitude etc.) are included in all HDF5 files (for internal team use) and PSA products (for public use). This page is intended to clarify certain aspects of how the geometry is calculated.

All geometry is calculated using SPICE kernels provided by the ESA SPICE service. Only reconstructed SPICE kernels are used, which delays data processing but means that the geometry values provided are the most accurate available.

Martian Year and Ls Calculation

Mars season is calculated using the SPICE routine lspcn. 

Light-time Corrections

No light-time or aberration corrections are applied to any geometry calculation. 

Mars Areoid and Digitial Shape Kernels

The Mars areoid altitude is interpolated from a 4 pixel per degree areoid model from MRO/MOLA (mgm1025). The megr90n000cb.bds Mars digital shape kernel is used to simulate the surface of Mars.

Negative Tangent Altitudes

Normal SPICE routines do not allow negative tangent altitudes to be calculated. We have adapted the tangent altitude calculation to allow these i.e. to record how far the tangent altitude goes below the surface of the planet.