Ionogram Information from the UK Solar System Data Centre at Chilton (RAL). Critical frequency is currently 3.1MHz (ie. foF2) and Maximum Usable Frequency MUF(D) is 8.13MHz. https://www.ukssdc.ac.uk/ionosondes/view_latest.html. Registration is required to access the data after which login just requires an email address (leave the password blank.
The RAL is the Rutherford Appleton Laboratory: https://stfc.ukri.org/about-us/where-we-work/rutherford-appleton-laboratory/
