GPS Constellation Energetic Particle Measurements

The Global Positioning System (GPS) is one of the most ubiquitously available services in the world used in military operations all the way down to locating a lost cat. However, GPS provides far more than just location and timing services; many of the satellites carry instruments to directly measure the space environment. On October 13th, 2016, the White House issued Executive Order #13744 `Coordinating Efforts to Prepare the Nation for Space Weather Events' which stated that responsible agencies `shall make historical data from the GPS constellation and other U.S. Government satellites publically available.' Los Alamos National Laboratory (LANL) has been designing, building, and operating energetic particle instruments in space for more than 50 years with two types of detectors on the current GPS constellation. As part of the 2016 Executive Order data collected by LANL sensors from 2001 through 2018 has been released and is archived by the National Oceanic and Atmospheric Administration. With more than 20 satellites operating LANL instruments during this period the dataset consists of more than 200 satellite-years of data that increases by roughly one satellite-year of data every two weeks and covers an entire solar cycle. The GPS constellation is in a medium-Earth orbit distributed across six orbital planes at a nominal altitude of ~20,200 km. Its circular orbit at an inclination of 55 degrees allows GPS to sample a wide range of magnetic latitude and McIlwain L. The data product consists of electron and proton measurements in energy ranges of 77 keV to and 10 MeV to respectively. These data are provided at a four minute cadence with information including differential omnidirectional fluxes, along with selected ephemeris data, count rates, as well as geomagnetic parameters computed from established magnetic field models. In comparison to the large number of GPS satellites, the average (even billion dollar) space mission will have one or maybe two satellites (with 5 being the outlier for the THEMIS mission). This exceptional data density allows the study of phenomena on rapid timescales and the simultaneous variations across magnetic local time. In depth study of how the magnetosphere reacts to solar storms and the access solar energetic particles have into the near-Earth environment is also possible. This will help in the verification and validation of transport codes as well as understanding what effect these solar events will have not only on our ground infrastructure, but our space assets as well. We will present an overview of the available data as well as some initial studies to exemplify its utility.