Minimize E1P-2

E1P-2 (Explorer-1 PRIME-2) / HRBE CubeSat Mission

E1P-2 (flight unit-2) is a CubeSat mission of MSU/SSEL (Montana State University / Space Science and Engineering Laboratory), Bozeman, MT, USA. The project is sponsored by the NASA Montana Space Grant Consortium based at MSU. The goal of the mission is to detect the Van Allen radiation belts in honor of the 50th anniversary of the Explorer-1 mission (launch January 31, 1958), America's first satellite that first discovered the cloud of highly energetic electrons trapped in the Earth's magnetic field. 1) 2) 3) 4)

Note: In early November 2011, shortly after launch, the E1P-2 mission was renamed to HRBE ( Hiscock Radiation Belt Explorer), in honor of Dr. William A. Hiscock, the founder and former director of the MSGC (Montana Space Grant Consortium) until his death in 2009. 5)

The science objective is to measure the intensity and variability of energetic electrons in LEO (Low Earth Orbit). E1P contributes to the development of the aerospace workforce by involving university students in spacecraft design, development , and operations.


Figure 1: Schematic view of the Van Allen radiation belts in relation to Earth (image credit: MSU)

Student involvement is required in all phases of the project:

• Design & development:

- All subsystems are developed in house

- Mentorship from SSEL staff

- Training in configuration and document management

- Training in good system engineering and design practices

- Training in fabrication & assembly practices.

• Testing:

- Design test plans and procedures

- Manage As-Runs

- Produce non-conformance reports and engineering change orders

- Validate and verify mission, system, subsystem level requirements

• Delivery:

- Support transport activities

- Conduct in house flight readiness reviews

- Support mission readiness reviews with CalPoly and NASA launch services program.

• Operations:

- Ham radio licensing

- Ground station training for principal operators

- Training program for local High School students as operators.

E1P-2 is a commemorative reflight of the E1P-1 (Explorer-1 PRIME-1) flight unit-1 mission of Montana State University. E1P-1 was launched on the ELaNa-1 sponsored mission of NASA on March 4, 2011 along with the CubeSats Hermes of the University of Colorado at Boulder, and KySat-1 of Kentucky Space. The primary payload of the mission was the Glory spacecraft of NASA. Unfortunately, the mission experienced a launch failure and ended in the Pacific Ocean. Telemetry indicated the fairing, the protective shell atop the Taurus XL rocket, did not separate as expected about three minutes after launch. 3) 6)

• The E1P-2 (flight unit-2) has been in parallel development since the summer of 2009 at MSU/SSEL. MSU delivered the E1P-2 to NASA in the summer 2011 for launch on the NPP mission from VAFB, CA. - The successful launch of this CubeSat is a most joyful experience and a great motivation for all at MSU involved in the development of the project.

• A previous CubeSat of MSU, called MEROPE (Montana Earth Orbiting Pico Explorer), experienced also a launch failure on a Dnepr-1 launch vehicle from Baikonur, Kazakhstan (launch July 26, 2006) along with many CubeSats and nanosatellites of other universities or institutions.

Table 1: Some background on the E1P CubeSat missions 6)


Figure 2: Artist's view of the deployed E1P-2 CubeSat in orbit (image credit: MSU/SSEL)



The spacecraft conforms to the 1U CubeSat standards, a cube volume with side lengths of 10 cm and a mass of ≤ 1 kg.

ACS (Attitude Control Subsystem): A passive magnetic attitude control system is used to align the GT perpendicular to the local magnetic field (Ref. 10).

• NiB Earth magnet assembly

• HyMu80 damping rod

• Centered near center of mass for optimal dynamic response.


Figure 3: Illustration of the ACS board (image credit: MSU/SSEL)

Attitude determination:

- The ratio of electrical current from adjacent solar panels is used to find the direction of the sun

- STK (Satellite Tool Kit) simulation until it matches the data.

EPS (Electrical Power Subsystem):

• 3.3 and 5 V regulators

• 2 Rose Li-ion batteries

• 6 solar arrays.


Figure 4: Photo of the EPS board (image credit: MSU/SSEL)

C&DH (Command and Data Handling) subsystem:

• Freescale MCU (HCSX12)

• Onboard flash data storage.

RF communications: A UHF transceiver is utilized for command and telemetry links (data rate = 1.2 kbit/s, modulation: FSK, KISS mode). In addition, a continuous telemetry beacon (435.505 MHz) is provided for real-time SOH and particle observations.

• Utilizes 2 CC1000 transceivers

• RF5110G amplifier

• Monopole antenna

• Tx: 437.505 MHz

• Rx: 437.305 MHz.


Figure 5: Photo of the communications subsystem (image credit: MSU/SSEL)


Figure 6: Schematic view of the E1P CubeSat architecture (image credit: MSU/SSEL)


Figure 7: Photo of the EIP-2 CubeSat (image credit: MSU/SSEL)


Launch: E1P-2 (Explorer-1 PRIME-2) was launched as a secondary payload to NASA's NPP (NPOESS Preparatory Project) spacecraft on October 28, 2011. The launch site was VAFB, CA. The launch vehicle was the Delta-2-7920-10 of Boeing, and the launch provider was ULA (United Launch Alliance).

Orbit: Sun-synchronous near-circular polar orbit (of the primary NPP), altitude = 824 km, inclination =98.7º, period = 101 minutes, LTDN (Local Time on Descending Node) at 10:30 hours. The repeat cycle is 16 days (quasi 8-day).

Secondary payloads: The secondary payloads on the NPP mission are part of NASA's ELaNa-3 (Educational Launch of Nanosatellites) initiative. All secondary payloads will be deployed from standard P-PODs (Poly Picosatellite Orbital Deployer). 7)

• AubieSat-1, a 1 U CubeSat of AUSSP (Auburn University Student Space Program), Auburn, AL, USA.

• DICE (Dynamic Ionosphere CubeSat Experiment), two nanosatellites (1.5U CubeSats) of the DICE consortium (Utah State University, Logan, UT, USA) with a total mass of 4 kg.

• E1P-2 (Explorer-1 PRIME-2) flight unit-2, a CubeSat mission of MSU (Montana State University), Bozeman, MT, USA.

• RAX-2 (Radio Aurora eXplorer-2), an NSF-sponsored 3U CubeSat of the University of Michigan, Ann Arbor, MI, USA

• MCubed (Michigan Multipurpose Minisat), a 1U CubeSat of the University of Michigan, Ann Arbor, MI. MCubed features also the collaborative JPL payload called COVE (CubeSat On-board processing Validation Experiment).

Orbit of the secondary payloads: After the deployment of the NPP primary mission, the launch vehicle transfers all secondary payloads into an elliptical orbit for subsequent deployment. This is to meet the CubeSat standard of a 25 year de-orbit lifetime as well as the science requirements of the payloads riding on this rocket. The rocket will take care of the maneuvering and when it reaches the correct orbit, it will deploy all of the secondary payloads, into an orbit of ~ 830 km x ~ 350 km, inclination = 99º.


Figure 8: Photo of AubieSat-1, E1P-2, and MCubed (from left) along with the P-POD prior to launch at VAFB (image credit: MSU/SSEL)



Status of mission:

• February 24, 2014: The HRBE CubeSat continues to operate nominally on orbit - achieving so far 28 months of operations (on Feb. 28, 2014). 8)

• In May 2013, the HRBE CubeSat and its payload are operating nominally, the project continues to collect engineering and science data.

Obviously, the HRBE and MCubed satellites remain in a conjunction since their orbital deployment from common P-POD. Both satellites are being tracked as one object (HRBE/MCubed). While the MCubed project of the University of Michigan is severely handicapped by this conjunction, the HRBE CubeSat is functioning nominally and seems to have not been adversely affected at all (by the conjunction of the two CubeSats).

The HRBE project is just as puzzled as others in this matter. HRBE is covered with solar panels on all 6 sides of the CubeSat - and nominal current draw and voltage is reported from all 6 panels. This means that by looking at just HRBE data, one would think that MCubed is not near HRBE at all. However, the the MSU project team assumes that there is a possibility that MCubed's deployable antenna may be stuck to the HRBE structure, therefore hindering their ability to transmit effectively. This would make sense that it is of some distance away from the HRBE panels and that HRBE would be getting sunlight on them most of the time. 9)

• The HRBE spacecraft and its payload are operating nominally in the summer of 2012. 10)

- 100% mission criteria success

- If the batteries should fail, the spacecraft can still be operated in the daylight orbit phase

- Up to August 2012, 47,000 beacons were decoded, ~ ½ of the data came from the HAM community

- 210 hours of science data have been collected so far.


Figure 9: Science coverage of HRBE (image credit: MSI/SSEL)

• Many lessons have been learned throughout the program to further the educational advancement of tomorrow’s space scientists and space engineers and to further the technological capabilities of very small satellites for application to space research. 11)

• In April 2012, there are continued nominal on-orbit operations of HRBE. As of April 28, 2012: 2563 orbits were completed. HRBE has been as complete success:

- .... as an educational tool. More than 100 students, and continuing

- .... as a demonstration of the utility of very small CubeSat satellites

- .... as a scientific platform. 12)

• In mid-February 2012, the HRBE CubeSat has now completed over 1500 orbits in LEO. 13)

- As of Feb. 15, 2012, the HRBE CubeSat had collected data for 111 days - surpassing the entire 111-day mission of its history-making predecessor, Explorer-1, the first successful U.S. satellite. 14)


Figure 10: Count Rates measured by the unidirectional detector on HRBE (image credit: MSU/SSEL, Ref. 11)

Legend to Figure 10: The CubeSat measurements were for selected passes between January 15 and February 15, 2012. The detector responds to locally mirroring electrons > 50 keV and protons > 500 keV.

• ”Turn-off” HRBE for MCubed/COVE commanding: January, 2012 (Ref. 12).

• Successful commanding from upgraded MSU Space Operations Center: January 13, 2012. Routine operations since January 2012 (Ref. 12).

• Successful commanding demonstrated from 18 m SRI dish: November 20, 2011 (Ref. 12).

• On Nov. 4, 2011, the E1P-2 CubeSat of MSU was renamed to HRBE (Hiscock Radiation Belt Explorer).


Figure 11: Illustration of the first hours after launch (image credit: MSU, Ref. 12)

• The project made contact with the spacecraft on October 29, 1011. All state of health levels were nominal, and the signal was loud and clear every pass. The operations team was able to get the satellite orientation information by looking at the solar array currents, and was able to judge how well the batteries were charging based on the array currents being negative, and the battery voltages were healthy. The temperatures were staying between 14-20ºC (within design limits). - Within three hours of launch, ham radio operators in France, England and The Netherlands had reported hearing from the satellite. 15)

• First reported receipt of beacon telemetry: L+162 min. University of Vigo, Vigo, Spain (Ref. 12) .

• Deployment into orbit from the P-POD: L+ 98 minutes, 45 seconds (Ref. 12).



Sensor complement:

E1P-2 employs a simple Geiger-Müller tube to monitor the flux of trapped electrons in the horns of the inner and outer radiation belts with energies greater than approximately 60 keV.

• The device seeks to monitor the temporal and spatial distribution of energetic electrons confined along magnetic field lines.

• Encounter radiation belt particles near the poles where magnetic field lines converge (the “horns”).


Figure 12: Photo of the Geiger tube (image credit: MSU/SSEL, Ref. 10)

Science payload:


• AmpTek amplifier

• Collimated tube to limit indirect particles from being counted.


Figure 13: Image of the NOAA POES SEM (Space Environment Monitor), image credit: David Evans, NOAA SEC

1) “MSGC Newsletter January 2012,” Feb. 1, 2012, URL:

2) David M. Klumpar, “The Utility of Very Small Satellites: Picosatellites and Nanosatellites for Science and Technology at Montana State University,” Nov. 5, 2009

3) Colorado Space Grant Consortium, Kentucky Space, Montana State University, “NASA’s ELaNa Program and it’s First CubeSat Mission,” Portland, ME, USA, Oct. 14-16,, 2010, URL:

4) David M. Klumpar, Keith W. Mashburn, “Developing the Explorer-1 [PRIME] Satellite for NASA’s ELaNa CubeSat Launch Program,” 8th Annual CubeSat Developer's Workshop, CalPoly, San Luis Obispo, CA, USA April 21-23, 2011, URL:

5) “MSU satellite renamed to honor Hiscock,” Bozeman News, Nov. 5, 2011, URL:


7) “CubeSat ELaNa III Launch on NPP Mission,” NASA, October 2011, URL:

8) Information provided by Dave Klumpar of MSU (Montana State University), Bozeman, MT, USA.

9) Information provided by Ehson Mosleh of MSU (Montana State University), Bozeman, MT, USA.

10) Matthew Handley and the HRBE Team, “The On-Orbit Performance of the HRBE (E1-P) CubeSat Nearing Nine Months in LEO,” 2012 Summer CubeSat Developers’ Workshop, Logan, Utah, USA, Aug. 11-12, 2012, URL:

11) David M. Klumpar, “CubeSat Lessons Learned: Two Launch Failures Followed by One Mission Success (Subtitle: What can go wrong will go wrong.),” Proceedings of the 26th Annual AIAA/USU Conference on Small Satellites, Logan, Utah, USA, August 13-16, 2012

12) David M. Klumpar, “The on-orbit Performance of HRBE (aka Explorer-1 [Prime] FU2,” 9th Annual Spring CubeSat Developer's Workshop, Cal Poly State University, San Luis Obispo, CA, USA, April 18-20, 2012, URL:

13) “JPL and Caltech Cubesat Proposals Move Forward,” Space Daily, Feb. 15, 2012, URL:

14) “MSU satellite surpasses goal; NASA taps MSU to queue up for another launch,” Space Daily, March 2, 2012, URL:

15) “MSU satellite orbits the Earth after early morning launch,” MSU, Oct. 28, 2011, URL:

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.