The Shuttle Radar Topogrpahy Mission
The best source of topographic data we have is data from the Shuttle Radar Topography Mission. This mission was flown in a matter of 10 days in 2000 with Space Shuttle Endeavour. The orbital inclination was 57 degrees. In principle, satellites can fly over the poles if the orbital inclination is close to 90 degrees. However, reaching a polar orbit requires more rocket fuel because the rotational velocity of the Earth that the rocket has at launch does not contribute to the orbital velocity for polar orbits (because a polar orbit is perpendicular to the ground velocity). Now, according to the journal article which reported on the mission:
The shuttle orbit of 233 km at 57° inclination was the highest possible for a fully loaded shuttle. (Farr et al., 2007)
So, all the fuel in the shuttle system (boosters, external and internal tank) was just enough to achieve a 57 degree orbit but a higher inclination was not possible. With this orbit, the mission managed to map all land between 56 degrees South and 60 degrees North (Farr et al., 2007).
A few examples of DEMs that go further North:
- ASTER GDEM V2 covers 99% of the Earth's land area, from 83 degrees South to 83 degrees North, at the same resolution as SRTM (30 meters).
- There's a DEM of Antarctica at 1 km resolution collected by CryoSat-2.
- ArcticDEM provides a DEM of Northern latitudes at 5 meter resolution.
Why no space agency has produced a truly global DEM with at least 30 m resolution is just a matter of speculation. But it probably comes down to: Not enough scientists begged for it and hence no money has been allocated for such a mission and later missions omitted the poles again because other conflicting requirements were more important.
Farr, T. G., Rosen, P. A., Caro, E., Crippen, R., Duren, R., Hensley, S., … Alsdorf, D. (2007). The Shuttle Radar Topography Mission. Reviews of Geophysics, 45(2). https://doi.org/10.1029/2005RG000183