Data from Release 53 of the Mars Exploration Rover mission is now online at the PDS Geosciences Node. This release includes APXS, Atmospheric Opacity, MI, Navcam, Pancam, and Rover Motion Counter data from sols 4591 through 4680 for the Opportunity rover.
I am the PI on a proposal to NASA PSTAR for a project that will collect digital data (predominantly still images and video) from Earth-based geological studies. I estimate about 3 Tb of data will be collected over 3 years. Our data will address operations of the Mars 2020 mission. I am wondering if the PDS Geosciences Node might be a suitable archive for our data.
You don't mention which of the three Mars Climate Sounder (MCS) data sets you are using. If you are looking for surface temperatures, you probably want to use the MCS DDR (Derived Data Record) data set. The primary documentation for this data set is here: https://atmos.nmsu.edu/PDS/data/MROM_2128/DOCUMENT/DP_SIS.PDF. To see if this is the right one, look at Table 2, which describes the columns in the data table. These data tables are ASCII text, so you can open them in any text editor or even in your browser. The columns are also described in a software-readable way in the "format files" in the LABEL directory of the archive, here: https://atmos.nmsu.edu/PDS/data/MROM_2128/LABEL/.
The other two MCS data sets are the RDR (Reduced Data Record) and EDR (Experiment Data Record). EDRs are raw data from the instrument sensors. RDRs are calibrated versions of the EDRs. Finally, the DDRs contain data converted to geophysical units, derived from the RDRs. For each of the three data sets, you'll find an overview of its contents in the file CATALOG/DATASET.CAT, a detailed description in the file DOCUMENT/DP_SIS.PDF, and complete column descriptions in *.FMT files in the LABEL directory. All these files are on the MCS archive volumes, which are hosted at the PDS Atmospheres Node at http://pds-atmospheres.nmsu.edu/data_and_services/atmospheres_data/Mars/Mars.html (scroll down to the MRO section).
I hope this is enough to get you started.
I am currently trying to find examples of the surface temperature on Mars, as taken by the Climate Sounder on the MRO, for the 3rd of August 2015. However, I'm very new at working with this data set and it is proving tricky. Firstly, there are a range of columns which mention "temp" in their title, however no amount of internet searching will tell me which one relates to actual ambient temperatures. Secondly, there should be some mention of Channels (aka Channel A. being measurements closest to the ground) but there isn't, so I'm not sure how to work out which data entries are from the surface. Thirdly, of all the temperature-related columns, none of them have data which varies by more than 1 degree throughout the 24 hour period, which suggests that they are actually referring to instrument temperatures rather than planetary temperatures. All in all, it is proving a tad difficult. The dataset was downloaded from Mars Orbita Datal Explorer.