As of 25 February 2023, C6 Forward processing of Terra and Aqua MODIS Land data products has been discontinued. The Collection 6.1 (C61) corrects these calibration issues and has a number of product specific improvements and enhancements that are listed in the C61 change document here. Data for C6.0 will remain available for six months, but the NSIDC encourages users to switch to the newer Collection 6.1 data.
The NSIDC DAAC provides access to the MODIS data and documentation at the following location: NSIDC DAAC MODIS Data Collection.