EQUULEUS (EQUilibriUm Lunar-Earth point 6U Spacecraft) and OMOTENASHI

EQUULEUS Spacecraft     Launch    Sensor Complement    OMOTENASHI   
OMOTENASHI Spacecraft     OMOTENASHI Mission Sequence    References

EQUULEUS, a deep-space 6U CubeSat mission, jointly proposed by JAXA (Japan Aerospace Exploration Agency) and the University of Tokyo to NASA, was selected as a secondary payload of the first flight of NASA's new SLS (Space Launch System) EM-1 mission. The spacecraft will be injected into a lunar flyby trajectory by the launch vehicle. The EQUULEUS project plans to demonstrate low-energy trajectory control techniques within the Earth-Moon region at EML2 (Earth—Moon L2 Lagrangian point 2), using a new water propulsion system with low thrust and little propellant, and to conduct scientific observations such as imaging Earth's plasmasphere. 1) 2)

NASA offered three CubeSat launch opportunities on EM-1 to international partners. Japan is providing two 6U CubeSats, EQUULEUS and the OMOTENASHI (Outstanding Moon Exploration Technologies Demonstrated by Nano Semi-Hard Impactor) whose size is about 10 x 20 x 30 cm with the mass of each CubeSat is limited to 14 kg. EQUULEUS will help scientists understand the radiation environment in the region of space around Earth by imaging Earth's plasmasphere and measuring the distribution of plasma that surrounds the planet. This opportunity may provide important insight for protecting both humans and electronics from radiation damage during long space journeys. It will also demonstrate low-energy trajectory control techniques, such as multiple lunar flybys, within the Earth-Moon region. 3) 4)




EQUULEUS is one of 13 cubesats planned to be carried with the Orion EM1 mission into a heliocentric orbit in cis-lunar space on the maiden flight of the SLS (Block 1) iCPS launch vehicle in 2020.


Figure 1: EQUULEUS will measure the distribution of plasma that surrounds the Earth to help scientists understand the radiation environment in the region of space around Earth. It will also demonstrate low-energy trajectory control techniques, such as multiple lunar flybys, within the Earth-Moon region (image credit: JAXA/University of Tokyo)


EQUULEUS mission overview:

The primary objective of the EQUULEUS mission is the demonstration of the trajectory control techniques within the Sun-Earth-Moon region (e.g. low-energytransfers using weak stability regions) for the first time by a nano-spacecraft. For this purpose, the spacecraft will fly to a libration orbit around the EML2 (Earth—Moon L2) Lagrangian point by using multiple LGAs (Lunar Gravity Assists). Figure 2 shows the current baseline trajectory, which includes three deterministic TCMs (Trajectory Correction Maneuvers) and three LGAs. 5) 6)


Figure 2: Current baseline trajectory of EQUULEUS from launch to EML2 (image credit: EQUULEUS collaboration)

After deployment into a lunar flyby trajectory, EQUULEUS will perform a deterministic TCM of 10-20 m/s to increase the perilune altitude and target an Earth-bound, Moonreturn trajectory. The first LGA occurs about a week after launch, then a sequence of lunar flybys is used to enable a low-energy transfer to an EML2 libration orbit. The sequence of lunar flybys can last several months and include one to four additional LGAs. At the end of this sequence, the spacecraft reaches the EML2 libration orbit. Finally, after completing the observation mission at EML2, the spacecraft leaves the Earth system on an escape orbit shortly before the completion of the onboard propellant. This engineering mission will demonstrate part of the future scenario of the utilization of the deep space port around the moon and its Lagrange points.

Design approach: The EQUULEUS trajectory is very challenging because of the fixed initial conditions , low thrust and Δv capabilities, and chaotic dynamics. The trajectory is split in a science phase, a forward transfer phase, and a backward transfer phase. In the science phase, we produce a database of thousands of quasi-periodic orbits around the Earth-Moon L2 libration point, computed in high-fidelity model with no deterministic maneuvers for at least 180 days, and evaluate their stability properties and station-keeping costs. 7) - A new approach is being developed to enforce the new science and flight system constraints. Figures 3 and 4 show an example 1:4 synodic resonant periodic orbit that avoids eclipses for six months and fulfill both of the science requirements for large windows of its period.


Figure 3: EQUULEUS science orbit in the Sun-Moon rotating frame (image credit: EQUULEUS collaboration)


Figure 4: Lunar night portion and altitude for the science orbit (image credit: EQUULEUS collaboration)

In the transfer phase, millions of potential transfer orbits will be computed, using the three degrees of freedom of the Δv1 to map the initial states into apogees, and from the halo orbits back to the same apogee (Ref. 7). For both the science and transfer phases, first guess solutions are generated patching trajectory bits computed in different models; the first guess solutions are then optimized by jTOP 8) in a high fidelity model that includes Earth, Sun and Moon ephemerides and low-order gravitational harmonics of the Earth and Moon.


EQUULEUS Spacecraft

EQUULEUS is a nanosatellite of the 6U CubeSat format designed jointly by JAXA (Japan Aerospace Exploration Agency) and the ISSL (Intelligent Space Systems Laboratory) of the University of Tokyo. It will measure the distribution of plasma that surrounds the Earth to help scientists understand the radiation environment in the region of space around Earth. It will also demonstrate low-energy trajectory control techniques, such as multiple lunar flybys, within the Earth-Moon Lagrangian point (EML2).

EQUULEUS is a three axis stabilized spacecraft powered by solar arrays. The spacecraft is equipped with the AQUARIUS (AQUA ResIstojet propUlsion System) propulsion system consisting of eight water thrusters also used for attitude control and momentum management. The spacecraft will carry ~1.5 kg of water, and the complete propulsion system occupies about 2.5 units out of the 6 units total spacecraft volume. AQUARIUS is a newly developed warm-gas propulsion system that uses water as propellant. The expected thrust is 3.3 mN and the Isp is 70 s; the spacecraft wet mass is 11.5 kg, including 1.22 kg of water that would provide about 77 m/s of Δv.

Most elements of the spacecraft utilize COTS (Commercial Off-The-Shelf) components, some are designed based on the experiences on the various past space missions. The project employed COTS components for the attitude control system and the solar array paddles. XACT-50 from Blue Canyon Technologies, which is an integrated unit of IRU (Inertial Reference Unit), STT (Star Tracker), RWs (Reaction Wheels), is used for the three-axis attitude control system, and HaWK (High Watts per Kilogram) from MMA, LLC, which are solar array paddles with a one-axis gimbal function; these components are used with some customization for the EQUULEUS mission.

Most of the bus components are based on the design of the PROCYON (Proximate Object Close flyby with Optical Navigation) mission and other 50 kg class Earth-orbiting microsatellites (note: PROCYON was an asteroid flyby space probe that was launched together with Hayabusa-2 on 4 December 2014). Electronics boards were redesigned to fit within the "CubeSat form factor". For example, the deep space X-band transponder which had been demonstrated on PROCYON was redesigned to significantly reduce its volume to fit within the CubeSat envelope (Figure 5).


Figure 5: The deep space X-band transponder demonstrated on PROCYON (left) and the newly developed transponder for EQUULEUS to fit within the CubeSat form factor (right). The function of the transponder was divided into multiple slices for the case of EQUULEUS (image credit: ISSL, JAXA)

The design of the mission instruments utilizes the experiences on the past space missions. The design of PHOENIX was optimized for EQUULEUS based on instruments onboard the previous space missions such as UPI (Upper Atmosphere and Plasma Imager) on Kaguya (SELENE mission), IMAP (Ionosphere, Mesosphere, upper Atmosphere, and Plasmasphere) of JAXA on ISS, and EXCEED on Hisaki [SPRINT-A (Spectroscopic Planet Observatory for Recognition of Interaction of Atmosphere)]. The electronics board of CLOTH was designed based on the ALADDIN (Arrayed Large-Area Dust Detectors in INterplanetary space) onboard the IKAROS solar sail demonstration mission. The image processing unit for DELPHINUS mission utilizes the image feedback control unit for the asteroid detection telescope for PROCYON.


Figure 6: External view of the deployed EQUULEUS nanosatellite (image credit: ISSL, JAXA)


Figure 7: Internal configuration of EQUULEUS (image credit: ISSL, JAXA)


Development status

• EQUULEUS was officially selected as one of the thirteen secondary payloads on SLS EM-1 in April 2016.16 The spacecraft is jointly developed by the University of Tokyo and JAXA. All of the system integration and electrical tests is conducted at the University of Tokyo. Part of the system-level environmental tests such as vibration and thermal vacuum tests are conducted outside of the University of Tokyo, e.g. CENT (Center for Nanosatellite Testing) at the Kyushu Institute of Technology, which is located in the western part of Japan.

- After the official selection, the development of the spacecraft engineering model (EM) started. System level environmental tests were completed by the end of 2017. The flight model (FM) design was made considering the EM test results, and the EQUULEUS project passed the CDR (Critical Design Review) in June 2018.

- Now the flight model manufacturing and integration is being conducted, aiming at the spacecraft ready for the launch in 2019.


Launch: The launch of the uncrewed EM-1(Exploration Mission-1) is expected in 2020 on the maiden test flight of NASA's SLS (Space Launch System). The launch will be from Launch Complex 39-B at the Kennedy Space Center, Cape Canaveral, FL. 9)




PHOENIX (Plasmaspheric Helium ion Observation by Enhanced New Imager in eXtreme ultraviolet)

PHOENIX will conduct the imaging of the Earth's plasmasphere in the EUV (Extreme Ultraviolet) wavelength range. The observations will be conducted throughout all mission phases and enhance the geospace in-situ observation conducted by the ERG (JAXA's small space science mission launched in 2016) and NASA's Van Allen probe missions. As a result, the project can improve our understanding of the radiation environment around the Earth, which is one of the critical issues for future human cis-lunar exploration. 10)


Figure 8: PHOENIX (EM) for the Earth plasmasphere imaging observation (image credit: ISSL, JAXA)

PHOENIX consists of multilayer-coated entrance mirror (diameter of 60 mm) and photon counting device (microchannel plate and resistive anode encoder), and electronics parts. The reflectivity of the mirror is optimized for the emission line of helium ion (wavelength of 30.4 nm) which is the important component of the Earth's plasmasphere. 11)

Scientific Objective: The Earth's plasmasphere is the region where dense plasma from the ionosphere is captured along the closed magnetic field lines. In the plasmasphere, it is known that various phenomena are caused by the electromagnetic disturbances in the solar wind. Helium ions are the second major component in the plasmasphere (almost 10% of the total amount), and resonantly scatter the solar EUV emission at the wavelength of 30.4 nm. By flying far from the Earth, PHOENIX provides the whole image of the Earth's plasmasphere to understand the spatial/temporal evolution of the plasmasphere.


Figure 9: PHOENIX imaging the Earth's plasmasphere (image credit: ISSL, JAXA)


CLOTH (Cis-Lunar Object detector within THermal insulation)

The objective of CLOTH is to detect and evaluate the meteoroid impact flux in the cis-lunar region by using dust detectors. The goal of this mission is to understand the size and spatial distribution of solid objects in the cislunar space.


DELPHINUS (DEtection camera for Lunar impact PHenomena IN 6U Spacecraft)

DELPHINUS will observe the impact flashes at the far side of the moon from EML2 for the first time. This observation will characterize the flux of impacting meteors, and the results will contribute to the risk evaluation for future human activity and/or infrastructure on the lunar surface. 12) 13)

Though DELPHINUS is one of the smallest celestial constellations, ranked 20th in size among 88 constellations, its shape consisting of five 4th stars is beautifully decorated in the summer constellation, and is next to EQUULEUS which is 2nd smallest constellation.

The DELPHENIUS instrument is an optical camera system whose main purposes are (1) to observe lunar impact flashes, and (2) to observe Near-Earth Objects (NEOs) such as asteroids, comets and Temporarily Captured Orbiters (TCOs or mini-moons).


Figure 10: DELPHINUS (EM) for the lunar impact flashes observation Image credit: ISSL, JAXA)

Lunar Impact Flash: Meteoroids are small rocky bodies traveling through interplanetary space. The various mass ranges of meteoroids ranging between 10-15 and 1015 grams are continuously colliding with the Earth-Moon system. Meteors are phenomena caused by the interaction of meteoroids with the Earth's upper atmosphere, while meteoroid's impact on the moon can be recognized by the optical flash of light produced when a meteoroid impacts the lunar surface. The influx rate of interplanetary dust onto the Earth-Moon surface is essential for understanding solar system evolution and is useful for the human space activities in the Cis-Lunar space, which is the volume within the Moon's orbit. Thus, it is very important to investigate size distributions, influx rate and daily variation of meteoroids.



OMOTENASHI (Outstanding MOon exploration TEchnologies demonstrated by NAno Semi-Hard Impactor)

OMOTENASHI means "hospitality" in Japanese. OMOTENASHI will demonstrate the technology for landing a 1 kg nano-lander on the Moon. The nano-lander and a 6 kg solid rocket motor will be ejected from the CubeSat. The solid rocket motor will be ignited to slow the nano-lander as it descends to the Moon. Before impact, the nano-lander will separate from the solid rocket motor and a two-lobed airbag will be deployed to cushion the landing, which will occur at a velocity of about 30 m/s. The nano-lander will take measurements of the lunar surface radiation environment and investigate soil mechanics using accelerometers. Very small landers such as OMOTENASHI could enable multi-point exploration.


Figure 11: Solid rocket motor and airbags separating from the OMOTENASHI CubeSat (image credit: JAXA, University of Tokyo)

OMOTENASHI is a 6U CubeSat of JAXA, one of thirteen CubeSats to be carried with the Orion EM-1 Exploration Mission-1) into a heliocentric orbit in cislunar space on the maiden flight of the NASA SLS (Space Launch System), scheduled to launch in 2020. The goal is to demonstrate low-cost technology for a semi-hard landing on the Moon's surface after being deployed into a lunar fly-by orbit by the SLS/ EM-1 spacecraft. 14)

OMOTENASHI is a challenging mission. One of the main challenges comes from trajectory, which must be robust to execution and navigation errors. A robust trajectory must have a small flight path angle (FPA) at Moon arrival. In particular, the project analysis found that it must satisfy -7º ≤ FPA ≤ 0º in order to be error-robust. To this end, the design of the different arcs of the trajectory cannot be performed independently, as they are strongly coupled.

After detaching from the SLS, OMOTENASHI must perform two deterministic maneuvers that will make this CubeSat the first one to perform a semi-hard landing on the Moon. A first maneuver, DV1 (Deceleration ΔV 1), will inject OMOTENASHI into a Moon-impacting orbit. After performing midcourse TCMs (Trajectory Correction Maneuvers) as needed, a solid rocket motor will be ignited shortly before the expected Lunar surface collision at a speed of approximately 2.5 km/s. After the deceleration maneuver (DV2), OMOTENASHI will experience a free-fall from a low height (close to 100 m) and arrive at the Moon surface with a speed of around 20 m/s. 15) 16)



In order to reduce the mass budget, OMOTENASHI is composed of an orbiting module, a retromotor module and a surface probe. The orbiting module must be ejected at rocket motor ignition to achieve the required deceleration. Finally, the surface probe will separate from the retromotor module at burnout to reduce the load on the energy absorption mechanisms.

Figure 12 shows the current state of the design of the spacecraft for different parts of the mission. On the top, Figure 12a shows the orbiting configuration of OMOTENASHI, featuring solar arrays in the +Y face. The solid rocket motor, including its sealing lid, is also visible. Before DV2, OMOTENASHI will deploy its airbag as can be seen in Figure 12b. The orbiting module is ejected after the solid rocket motor ignition, being the configuration during the deceleration maneuver as shown in Figure 12c.


Figure 12: OMOTENASHI configuration at different parts of the mission (image credit: JAXA, University of Tokyo)


Figure 13: The OMOTENASHI Engineering Model was assembled in January 2018 (image credit: JAXA, University of Tokyo) 17)

A detailed view of the internal parts of OMOTENASHI is presented in Figure14. Figure 14a shows the RCS (Reaction Control System), attitude control module, communication devices, rocket motor and surface probe. Looking from a different angle, Figure 14b shows the battery module, the laser diode (LD) used to ignite the motor, and the devices in charge of inflation of the airbag: CO2 gas tank and shape memory allow (SMA) opener.


Figure 14: OMOTENASHI subsystems detailed view (image credit: JAXA, University of Tokyo)


Trajectory overview

OMOTENASHI introduces a unique approach for lunar landing. Traditionally, lunar landing missions are characterized by an Earth-Moon transfer and lunar orbit insertion, followed by the descent, hovering and landing phases. This approach allows for a flexible design, as the errors in all phases can be detected and corrected, but requires a full set of sensors and a large, restartable propulsion systems, both of which are not available to small satellites. OMOTENASHI combines the maneuvers for the lunar orbit insertion, descent and landing into a single maneuver executed by a solid rocket motor, followed by a free-fall onto the lunar surface with impact speed on the order of 30 m/s. If proven to work, the OMOTENASHI approach will enable an entirely new class of lunar exploration missions by small satellites, also exploiting more ride-share opportunities from the planned Lunar Orbital Platform-Gateway.

In order to design a trajectory that leads to a safe semi-hard landing on the surface of the moon, the trajectory is divided in two arcs: the transfer and the landing phase.

During the transfer phase, OMOTENASHI must modify its orbit from the Moon fly-by injection orbit to a Moon intersection orbit. 18) Additionally, health check-ups and orbit determination are key aspects of this phase. OD (Orbit Determination) is a critical resource during the first hours of operation, as the 13 delivered cubesats have the same need of accurately assessing the orbit they are flying, and the time before the Moon fly-by/arrival is limited. During the trajectory design process, this was identified as one of the key aspects that the small satellite community should address in the near future.

The landing phase starts minutes before arriving at the Moon surface, and the main event is the deceleration of the spacecraft by the use of a solid rocket motor. 19) Another important aspect is that in order to successfully deliver the required deceleration ΔV , the orbiter module will be detached from the rest of the spacecraft to reduce the mass to be decelerated.

In the absence navigation and maneuver execution errors, any Moon-intersecting trajectory would lead to a successful landing, provided that the surface probe can absorb the residual kinetic energy after braking. However, the uncertainty on the actual trajectory introduces very strong constraints between the two phases.

From the point of view of a safe landing, a trajectory with a very shallow FPA is preferred to minimize the effect of timing errors on the vertical displacement of the spacecraft. A high position error on the vertical direction may lead to a premature landing during the solid rocket motor burn, jeopardizing the mission. On the other hand, a very shallow FPA might cause missing the Moon in the presence of errors. To reduce the fly-by probability, a TCM may be introduced if necessary. A TCM must be carefully planned in order not to hinder the orbit accuracy during the landing, as it reduces the time to perform OD before the landing phase.

The current analysis and design were conducted with the initial conditions provided by NASA/MSFC (Marshall Space Flight Center) 20) and shown in Table 1. The position and velocity components are expressed in a Moon-centered reference frame whose axes are parallel to the J2000 Ecliptic frame. We considered the Sun, Earth and Moon Gravity as point masses and an impulsive DV1 maneuver. In the future solar radiation pressure, spherical harmonics and finite burns will be included, but the results will not qualitatively change.


2018 Oct 07 15:39:16

x (km)


y (km)


z (km)


vx (km/s)


vy (km/s)


vz (km/s)


Table 1: Initial conditions expressed in the Moon-centered J2000 Ecliptic frame

Figure 15 shows the transfer trajectory in an Earth-centered frame that rotates with the Moon. Figure 16 shows the landing phase trajectory, including the deceleration and final free-fall. One day after separation, Δv1 is executed by a cold-gas jet system to correct for launcher dispersions errors and to target a lunar landing orbit, with shallow flight path angle at approach on a visible landing site. Depending on the launch geometry, Δv1 can be 5-16 m/s; a trajectory correction maneuver is also planned to correct for Δv1 execution errors and knowledge errors. Shortly before impact, the solid motor executes a maneuver of about 2500 m/s to bring the spacecraft almost to a stop, which is followed by a free fall onto the lunar surface. The semi-hard landing is enabled by a shock absorption mechanisms which allows up to 30 m/s impact vertical velocity, corresponding to a few hundreds meters of free fall.


Figure 15: Transfer phase (image credit: JAXA, University of Tokyo)


Figure 16: Landing phase (image credit: JAXA, University of Tokyo)

OD (Orbit Determination)

Navigation accuracy plays a critical role in the success of a lunar lander like OMOTENASHI. In the first place, the strong FPA constraints at Moon arrival demand a precise knowledge of the state vector of the satellite at DV1. Moreover, vertical position errors during landing may lead to an early impact with the Moon while the solid motor rocket maneuver is being performed. Timing errors during landing could also jeopardize the mission, even if the approach trajectory is characterized by a small FPA.

Moreover, the actual trajectory has a strong influence in the position accuracy at Moon arrival. We observed differences up to one order of magnitude in the vertical position error at landing when following different orbits for the same tracking strategy. However, a small-satellite operator has in most cases limited control over the orbit he is being deployed into. Thus, great care must be taken when designing the OD strategy to be employed.

In summary, the design of the transfer phase, including a cold gas maneuver to target the Moon and a trajectory correction maneuver, was introduced. After the transfer phase, a deceleration maneuver using a solid rocket motor, reaching a final zero vertical-velocity and a specified height over the Moonsurface, will be followed by a ballistic free-fall.

All error sources were identified and characterized. Deviations from the nominal trajectory were studied and the most critical contributions were determined, which in turn allows to propose requirements to the design of the related subsystems in order to increase the success rate of the transfer and landing phases of OMOTENASHI.

The analysis of the landing phase shows the need of a trajectory correction maneuver to compensate for execution errors of the deterministic maneuver. Orbit Determination requirements can also be drawn from this study, and we determined that OMOTENASHI must request support from international partners in order to use their ground stations for a safe landing.

Simulation results of the landing phase identify several critical error sources that should be further studied in order to increase the landing success rate: structural limit of the landing devices and accuracy of attitude and solid rocket engine. This is currently being considered by the OMOTENASHI team. Additionally, we found that employing DDOR (Delta-Differential One-way Ranging) tracking is paramount to reduce the vertical position error at Moon landing, which could jeopardize the mission.

The effect of the flight path angle at Moon arrival was also studied. It was found that for this kind of mission it is necessary to design a shallow flight path angle trajectory, shallower than -7º. This imposes constraints on the design of the transfer phase, which becomes strongly coupled with the landing phase.

In future work, and before OMOTENASHI is launched, there are some additional tasks that OMOTENASHI trajectory team must address in their work. This includes further refinement of the dynamical model (i.e. including spherical harmonics, finite thrust burns for the cold gas thruster and solar radiation pressure). In addition, the robustness of the entire trajectory should be studied, since in the present work they are analyzed separately.



OMOTENASHI: Mission Sequence

• Total of 2 orbital maneuvers, DV1, DV2

• Attitude spin maneuver before deceleration

• Deceleration until "some" (~100-200 m) altitude above the lunar surface

• Free fall to the surface with low vertical speed.



Figure 17: Overview of the OMOTENASHI mission sequence steps (image credit: JAXA)

Parameters of the OMOTENASHI spacecraft: 21)

• Total mass of spacecraft: 14 kg

• Orbiting Module (OM) = 8.6 kg (excl. RM and SP). OM carries all spacecraft bus and payloads

• Retro Motor: 4.4 kg (excl. OM and SP)

• RM is the solid motor that decelerates the CubeSat to the lunar surface.
Note: In the current design Surface probe is not separated from the solid rocket motor, though it will be separated by the impact shock. Current maximum impact velocity will be about 50 m/s. 22)


Figure 18: Spacecraft configuration of OMOTENASHI (image credit: JAXA)


Figure 19: RM (Rocket Motor) configuration (image credit: JAXA)


Figure 20: What finally lands on the lunar surface is the SP (Surface Probe) with a mass of 0.7 kg (image credit: JAXA)

SP carries the landing structure and the transponder for communication (P-band), along with OBC and Power system (Li – 18 Wh).



Overview of secondary payloads on the Orion/EM-1 mission

The first flight of NASA's new rocket, SLS ( Space Launch System), will carry 13 CubeSats/Nanosatellites to test innovative ideas along with an uncrewed Orion spacecraft in 2020. These small satellite secondary payloads will carry science and technology investigations to help pave the way for future human exploration in deep space, including the journey to Mars. SLS' first flight, referred to as EM-1 (Exploration Mission-1 ), provides the rare opportunity for these small experiments to reach deep space destinations, as most launch opportunities for CubeSats are limited to low-Earth orbit. 23) 24)

The secondary payloads, 13 CubeSats, were selected through a series of announcements of flight opportunities, a NASA challenge and negotiations with NASA's international partners.


NASA selected two payloads through the NextSTEP (Next Space Technologies for Exploration Partnerships) Broad Agency Announcement of May 5, 2015:

LunIR ⟨originally called Skyfire) - Lockheed Martin Space Systems Company, Denver, Colorado, will develop a 6U CubeSat to perform a lunar flyby of the moon, taking sensor data during the flyby to enhance our knowledge of the lunar surface. LunIR will test a new technology mid-wave infrared camera and micro-cryocooler. LunIR also includes a visible imager.

Lunar IceCube - Morehead State University, Kentucky, will build a 6U CubeSat to search for water ice and other resources at a low orbit of only 62 miles above the surface of the moon. This CubeSat will orbit the Moon and prospect for water and other volatiles in lunar regolith using BIRCHES (Broadband Infrared Compact High-Resolution Exploration Spectrometer) developed at NASA/GSFC.

Three payloads were selected by NASA's Human Exploration and Operations Mission Directorate:

NEA Scout (Near-Earth Asteroid Scout), the 6U CubeSat of NASA/MSFC/JPL will perform reconnaissance of an asteroid, take pictures and observe its position in space

BioSentinel - a 6U CubeSat of NASA/ARC will use yeast to detect, measure and compare the impact of deep space radiation on living organisms over long durations in deep space.

Lunar Flashlight - a 6U CubeSat of NASA/JPL/MSFC will look for ice deposits and identify locations where resources may be extracted from the lunar surface

Two payloads were selected by NASA's Science Mission Directorate:

CuSP – a 6U CubeSat of the SwRI (Southwest Research Institute) "space weather station" to measure particles and magnetic fields in space, testing the practicality for a network of stations to monitor space weather

LunaH-Map a 6U CubeSat of Arizona State University will map hydrogen within craters and other permanently shadowed regions throughout the moon's south pole

Three additional payloads were determined through NASA's Cube Quest Challenge – sponsored by NASA's Space Technology Mission Directorate and designed to foster innovations in small spacecraft propulsion and communications techniques. CubeSat builders will vie for a launch opportunity on SLS' first flight through a competition that has four rounds, referred to as ground tournaments, leading to the selection in 2017 of the payloads to fly on the mission.

Cislunar Explorers, Cornell University, Ithaca, New York. Cislunar Explorers' concept consists of a pair of spacecraft on a mission to orbit the moon. These two spacecraft are mated together as a 6U CubeSat. After deployment from the launch vehicle, they will split apart and each give their initial rotation in the process of decoupling.

CU-E3(CU Earth Escape Explorer), a 6U CubeSat of the University of Colorado in Boulder, CO. The CU-E3 mission will use a lunar gravity assist maneuver to place the CubeSat in a heliocentric orbit that trails the Earth at a distance > 1AU (Astronomical Unit). The distance between the Earth and the spacecraft will gradually increase over time, reaching 27 million km by the end of its one-year mission.

Team Miles, Team Miles is led by the company Fluid and Reason LLC. Team Miles is a group of citizen scientists and engineers that initially came together through Tampa Hackerspace in Florida – all participants in the community, nonprofit workshop. Team Miles is a 6U CubeSat to demonstrate navigation in deep space using innovative plasma thrusters. Use of a software defined S-band radio to communicate with Earth.

NASA has also reserved three slots for payloads from international partners. These are: 26)

EQUULEUS (EQUilibriUm Lunar-Earth point 6U Spacecraft) of ISSL (Intelligent Space Systems Laboratory) of the University of Tokyo and JAXA. EQUULEUS will help scientists understand the radiation environment in the region of space around Earth by imaging Earth's plasmasphere and measuring the distribution of plasma that surrounds the planet. This opportunity may provide important insight for protecting both humans and electronics from radiation damage during long space journeys. It will also demonstrate low-energy trajectory control techniques, such as multiple lunar flybys, within the Earth-Moon region.

OMOTENASHI (Outstanding MOon exploration TEchnologies demonstrated by NAno Semi-Hard Impactor) of JAXA. JAXA will use the OMOTENASHI to demonstrate the technology for low-cost and very small spacecraft to explore the lunar surface. This technology could open up new possibilities for future missions to inexpensively investigate the surface of the moon. The CubeSat will also take measurements of the radiation environment near the moon as well as on the lunar surface.

ArgoMoon. The Italian company Argotec is building the ArgoMoon CubeSat under the Italian Space Agency (ASI) internal review and approval process. ArgoMoon will demonstrate the ability to perform operations in close proximity of the ICPS ( Interim Cryogenic Propulsion Stage), which will send Orion onto its lunar trajectory. It should also record images of the ICPS for historical documentation and to provide valuable mission data on the deployment of other CubeSats. Additionally, this CubeSat should test optical communication capabilities between the CubeSat and Earth.

Table 2: Overview of the 10 selected US secondary missions for the inaugural Orion/EM-1 test flight plus three CubeSats from international partners 25) 26)

All the CubeSats will ride to space inside the Orion Stage Adapter, which sits between the ICPS ( Interim Cryogenic Propulsion Stage) and Orion (Figure 21). The cubesats will be deployed following Orion separation from the upper stage and once Orion is a safe distance away.

The SPIE ( Spacecraft and Payload Integration and Evolution) office is located at NASA/MSFC (Marshall Space Flight Center) in Huntsville, Alabama, which handles integration of the secondary payloads.

These small satellites are designed to be efficient and versatile—at no heavier than 14 kg, they are each about the size of a boot box, and do not require any extra power from the rocket to function. The science and technology experiments enabled by these small satellites may enhance our understanding of the deep space environment, expand our knowledge of the moon, and demonstrate technology that could open up possibilities for future missions. 27)

A key requirement imposed on the EM-1 secondary payload developers is that the smallsats do not interfere with Orion, SLS or the primary mission objectives. To meet this requirement, payload developers must take part in a series of safety reviews with the SLS Program's Spacecraft Payload Integration & Evolution (SPIE) organization, which is responsible for the Block 1 upper stage, adapters and payload integration. In addition to working with payload developers to ensure mission safety, the SLS Program also provides a secondary payload deployment system in the OSA (Orion Space Adapter). The deployment window for the CubeSats will be from the time ICPS disposal maneuver is complete (currently estimated to require about four hours post-launch) to up to 10 days after launch. 28)


Figure 21: The CubeSats will be deployed from the Orion Stage Adapter (image credit: NASA, Ref. 24)


1) "EQUULEUS - From Japan to EML2," URL:

2) Stefano Campagnola, Javier Hernando-Ayuso, Kota Kakihara, Yosuke Kawabata, Takuya Chikazawa, Ryu Funase, Naoya Ozaki, Nicola Baresi, Tatsuaki Hashimoto, Yasuhiro Kawakatsu, Toshinori Ikenaga, Kenshiro Oguri, Kenta Oshima, "Mission analysis for the EM-1 CubeSats EQUULEUS and OMOTENASHI," Proceedings of the 69th IAC (International Astronautical Congress) Bremen, Germany, 1-5 October 2018, paper: IAC-18-B4.8.2, URL:,B4,8,2,x45356.pdf

3) "International Partners Provide Science Satellites for America's Space Launch System Maiden Flight," NASA, May 26, 2016, URL:

4) Christopher Moore, Jitendra Joshi, Nicole Herrmann, "Deep-Space CubeSats on Exploration Mission -1," Proceedings of the 68th IAC (International Astronautical Congress), Adelaide, Australia, 25-29 Sept. 2017, paper: IAC-17-B4.8

5) Ryu Funase, Satoshi Ikari, Yosuke Kawabata, Shintaro Nakajima, Shunichiro Nomura, Kota Kakihara, Ryohei Takahashi, Kanta Yanagida, Shuhei Matsushita, Akihiro Ishikawa, Nobuhiro Funabiki, Yusuke Murata, Ryo Suzumoto, Toshihiro Shibukawa, Daiko Mori, Masahiro Fujiwara, Kento Tomita, Hiroyuki Koizumi, Jun Asakawa, Keita Nishii, Ichiro Yoshikawa, Kazuo Yoshioka, Takayuki Hirai, Shinsuke Abe, Ryota Fuse, Masahisa Yanagisawa, Kota Miyoshi, Yuta Kobayashi, Atsushi Tomiki, Wataru Torii, Taichi Ito, Masaki Kuwabara, Hajime Yano, Naoya Ozaki, Toshinori Ikenaga, Tatsuaki Hashimoto, "Flight Model Design and Development Status of the Earth―Moon Lagrange Point Exploration CubeSat EQUULEUS Onboard SLS EM-1," Proceedings of the 32nd Annual AIAA/USU Conference on Small Satellites, Logan UT, USA, Aug. 4-9, 2018, paper: SSC18-VII-05, URL:

6) "EQUULEUS Trajectory Control Demonstration within Sun-Earth-Moon Region," URL:

7) Kenta Oshima, Stefano Campanola, Chit Hong Yam, Yuki Kayama, Yasuhiro Kawakatsu, Naoya Ozaki, Quentin Verspieren, Kota Kakihara, Kenshiro Oguri, Ryu Funase, "EQUULEUS Mission Analysis: Design of the Transfer Phase," 31st ISTS conference paper, June 2017, URL:

8) S. Campagnola, N. Ozaki, Y. Sugimoto, C. C. H. Yam, H. Chen, S. Ogura, B. Sarli, Y. Kawakatsu, R. Funase, S. Nakasuka, Y. Sugimoto, Y., Kawakatsu, H. Chen, Y. Kawabata, "Low-Thrust trajectory design and operations of procyon, the first deep-space micro-spacecraft," 24th International Symposium on Space Flight Dynamics, Munich, Germany, Vol. 7, 2015. ISSN 00741795.

9) Philip Sloss, "EM-1 Update: Making progress, but still behind schedule," NASA, 3 April 2018, URL:

10) "EQUULEUS - From Japan to EML2," URL:

11) "Plasmaspheric Helium ion Observation by Enhanced New Imager in eXtreme ultraviolet," URL:

12) Ryota Fuse, "The study of the space based observation of lunar impact flashes", 31st ISTS (International Symposium on Space Technology and Science), paper: 2017-s-15-k, Matsuyama, Japan, 3-9 June 2017


14) Javier Hernando-Ayuso, Yusuke Ozawa, Shota Takahashi, Stefano Campagnola, Toshinori Ikenaga, Tomohiro Yamaguchi, Tatsuaki Hashimoto, Chit Hong Yam, Bruno V. Sarli, "Trajectory Design for the JAXA Moon Nano-Lander OMOTENASHI," Proceedings of the 31st Annual AIAA/USU Conference on Small Satellites, Logan UT, USA, Aug. 5-10, 2017, paper: SSC17-III-07, URL:

15) T. Hashimoto, T. Yamada, J. Kikuchi, M. Otsuki, T. Ikenaga, "Nano Moon Lander: OMOTENASHI," 31st ISTS (International Symposium on Space Technology and Science), paper: 2017-f-053, Matsuyama, Japan, 3-9 June 2017

16) S. Campagnola, N. Ozaki, J. Hernando-Ayuso, K. Oshima,T. Yamaguchi, K. Oguri,Y. Ozawa, T. Ikenaga, K. Kakihara, S. Takahashi, R. Funase, Y. K. T. Hashimoto, "Mission Analysis for EQUULEUS and OMOTENASHI", 31st ISTS (International Symposium on Space Technology and Science), paper: 2017-f-044, Matsuyama, 3-9 June Japan, 2017.


18) Y. Ozawa, S. Takahashi, J. Hernando-Ayuso, S. Campagnola, T. Ikenaga, T. Yamaguchi, B. Sarli, "OMOTENASHI Trajectory Analysis and Design: Earth-Moon Transfer Phase", 31st ISTS (International Symposium on Space Technology and Science), paper: 2017-f-054, Matsuyama, Japan, 3-9 June 2017.

19) J. Hernando-Ayuso, S. Campagnola, T. Ikenaga, T. Yamaguchi, Y. Ozawa, B. V. Sarli, S. Takahashi, C. H. Yam, "OMOTENASHI Trajectory Analysis and Design: Landing Phase", 26th International symposium on Space Flight Dynamics, held together the 31st ISTS (International Symposium on Space Technology and Science), paper: 2017-d-050, Matsuyama, Japan, 3-9 June 2017

20) R. Stough, "REVISED - Delivery of Interim October 7th 2018 Launch Post ICPS Disposal State Vectors for Secondary Payload Assessment", Technical report, George C. Marshall Space Flight Center, NASA, 2016

21) Onur Çelik, Tatsuaki Hashimoto, Ryu Funase, Yasuhiro Kawakatsu, Stefano Campagnola, Toshinori Ikenaga,"Overview of Japanese Lunar CubeSats OMOTENASHI & EQUULEUS," UN/South Africa Symposium on Basic Space Technology, Stellenbosch, South Africa, 11-15 December 2017, URL:

22) Information provided by Tatsuaki Hashimoto of JAXA

23) Kathryn Hambleton, Kim Newton, / Shannon Ridinger, "NASA Space Launch System's First Flight to Send Small Sci-Tech Satellites Into Space," NASA Press Release 16-011, Feb. 2, 2016, URL:

24) Christopher Moore, Jitendra Joshi, Nicole Herrmann, "Deep-Space CubeSats on Exploration Mission-1," Proceedings of the 68th IAC (International Astronautical Congress), Adelaide, Australia, 25-29 Sept. 2017, paper:IAC-17-B4.8

25) "Three DIY CubeSats Score Rides on NASA's First Flight of Orion, Space Launch System," NASA Release 17-055, 8 June 2017, URL:

26) Kathryn Hambleton, Kim Henry, Tracy McMahan, "International Partners Provide Science Satellites for America's Space Launch System Maiden Flight," NASA, 26 May 2016 and update of 07 February 2018, URL:

27) "Smallsats Of Scientific Persuasions To Be Supplied By International Partners To NASA For The Maiden Flight Of SLS," Satnews Daily, May 31, 2016, URL:

28) Kimberly F. Robinson, Scott F. Spearing, David Hitt, "NASA's Space Launch System: Opportunities for Small Satellites to Deep Space Destinations," Proceedings of the 32nd Annual AIAA/USU Conference on Small Satellites, Logan UT, USA, Aug. 4-9, 2018, paper: SSC18-IX-02, 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 (

EQUULEUS Spacecraft     Launch    Sensor Complement    OMOTENASHI   
OMOTENASHI Spacecraft     OMOTENASHI Mission Sequence    References    Back to top