The following information obtained from UNAVCO's online DOI system:
(https://www.unavco.org/data/doi/search/search.html)

MAGNET - SLT1-SLT1 P.S.
Start: 30-Jan-2013
End: 21-Jun-2018
Blewitt, Geoff, Hammond, William C., Kreemer, Corne, 2013, MAGNET - SLT1-SLT1 P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T56971S5