I’m also interested in investigating ways in which we can combine cosmological surveys to maximise the amount we learn from them. Observational cosmologists look to the biggest and best telescope surveys to provide data which we use to test our theories. Regardless of how ‘cutting-edge’ a telescope is, each will still have a weakness. An area of its design which another telescope can out-perform it in. By combining the data from different telescopes you mitigate these weaknesses and can limit telescope-specific systematics.
Take an example where we have both an optical and a radio telescope:
[Credit: lsst.org & skatelescope.org]
Firstly consider using the optical telescope on its own – its auto-correlation function is given by:
The final result leaves you with a noise-noise term which will impact your data. If we instead choose to cross-correlate with another telescope, our radio telescope, then the correlation function will be:
Here we can assume we lose the noise-noise term since both telescope systematics will be uncorrelated due to the difference in telescope design. This is a basic demonstration of some of the power behind telescope synergies.
Calibrating Photometric Redshifts with HI Intensity Maps