E1P logo showing the satellite orbiting around Earth with North America front and centerRendering of E1P in orbit around the Earth

Mission Overview

The Hiscock Radiation Belt Explorer (HRBE), named in honor of Dr. William A. Hiscock, founder of the Montana Space Grant Consortium, launched from Vandenberg Airforce Base in California on October 28, 2011. Formerly known as Explore-1 [PRIME] (E1P), the Cubesat-class satellite was developed in the Space Science and Engineering Laboratory (SSEL) at Montana State University.

HRBE's mission was to detect and characterize the Van Allen radiation belts in honor of the 50th anniversary of Explorer-1, America's first satellite. Explorer-1 first discovered the cloud of highly energetic electrons trapped in the Earth's magnetic field. HRBE carried a miniature Geiger tube donated by Dr. Van Allen to measure the intensity and variability of these electrons from low earth orbit.

Spacecraft Overview

Cutaway of E1P showing the internal layout with labelsCutaway rendering of E1P.

HRBE was a 1U CubeSat that was designed and built by SSEL students at Montana State University. This 10x10x10 cm cube had an aluminium structure with 2 solar cells on each side for power generation. The spacecraft bus consisted of a Command and Data Handling (CDH) board for controlling the flow of data throughout the satellite; an Electrical Power System (EPS) for regulating power from the solar panels and charging the batteries; a UHF transceiver for sending and receiving data to and from the ground; and a passive Attitude Control System (ACS). The payload was a small Geiger Müller tube which detected energetic particles trapped in Earth’s magnetic field.


Explore-1 [Prime] Flight Unit 1 was launched as a secondary payload with NASA’s Glory satellite on March 4, 2011 as part of the ELaNa-I mission. Unfortunately, during launch the Taurus XL rocket’s payload fairing failed to separate on schedule leaving the vehicle unable to achieve orbit due to its excess mass. E1P Flight Unit 1, along with several other university CubeSats were deployed from the launch vehicle, but fell back to Earth soon after.

Explore-1 [Prime] Flight Unit 2 was launched as a secondary payload with NOAA’s NPP satellite on October 28, 2011 as part of the ELaNa-III mission. HAM operators around the world, as well as SSEL’s K7MSU ground station, were able to decode E1P Flight Unit 2’s beacon soon after launch. Following the launch, E1P Flight Unit 2 was renamed the Hiscock Radiation Belt Explorer (HRBE) in honor of Dr. William A. Hiscock, founder of the Montana Space Grant Consortium.

Long exposure of the launch arc from the Delta II rocket that carried E1P

Launch arc from the Delta II carrying E1P Flight Unit 2. Image Credit: NASA/Bill Ingalls

It was quickly discovered that SSEL could not command HRBE, due to the width of the front-end receiver. To compensate for the wide front end, the ground station was upgraded to include a 1.5-kW UHF amplifier in January 2012.

As of 2018, SSEL no longer commands HRBE, having upgraded the ground station for the FIREBIRD, FIREBIRD II, and IT-SPINS missions, but the satellite continues to occasionally beacon to this day.