SELENE (Kaguya)

SELENE (Kaguya)
Name	SELENE (Kaguya)
Mission type	Lunar exploration
Operator	Japan Aerospace Exploration Agency
Launch date	2007-09-14
Launch vehicle	H-IIA
Launch site	Tanegashima Space Center
Manufacturer	Institute of Space and Astronautical Science
Mass	2914 kg (launch mass)
Orbit	Lunar polar orbit

SELENE (Kaguya)

SELENE (Kaguya) was a Japanese lunar orbiter developed by the Japan Aerospace Exploration Agency and the Institute of Space and Astronautical Science launched on 14 September 2007 aboard an H-IIA rocket from Tanegashima Space Center. The mission complemented contemporaneous efforts by NASA's Lunar Reconnaissance Orbiter, European Space Agency missions, and historical programs such as the Apollo program and Luna programme, contributing to global lunar science and exploration planning. SELENE combined remote sensing, geophysical experiments, and technology demonstration to map the Moon's surface, gravity field, and exosphere.

Overview

SELENE was designed as a flagship robotic mission by the Japan Aerospace Exploration Agency to produce high-resolution topography, gravity, mineralogical mapping, and plasma/particle environment data for the Moon. The project involved collaborations with institutions including the National Astronomical Observatory of Japan, JAXA, and international partners such as NASA, CNES, and research groups associated with Massachusetts Institute of Technology, University of Tokyo, and Kyoto University. The mission architecture used a main orbiter with two small sub-satellites to obtain stereo imagery and gravity data, addressing objectives relevant to future robotic and crewed efforts exemplified by programs like Artemis program and lessons from Soviet Union's Luna programme.

Mission History

SELENE's development traces to Japan's post-Space Shuttle Challenger era expansion in robotic planetary exploration, formalized under JAXA's mid-1990s strategic plans alongside projects such as Hayabusa. Following approval, SELENE underwent integration and testing at facilities associated with the Institute of Space and Astronautical Science and was launched by Mitsubishi Heavy Industries. After translunar injection, SELENE performed lunar insertion and deployed the small satellites named Okina (Rstar) and Ouna (Vstar). The spacecraft executed phased operations, entering polar orbit, conducting commissioning, and commencing routine science campaigns while coordinating data downlink via ground stations including Usuda Deep Space Center and international tracking assets.

Spacecraft Design and Instruments

The SELENE stack comprised a Main Orbiter, a Relay/Radio Science Sub-satellite (Okina), and a VLBI/Relay Sub-satellite (Ouna). The Main Orbiter carried instrument suites developed by teams from Nagoya University, Osaka University, and University of Tokyo: the Lunar Radar Sounder, Terrain Camera, Multiband Imager, X-ray Spectrometer, Gamma-Ray Spectrometer, and a Microwave Radiometer. The mission included a radio science experiment to map the lunar gravity field using Doppler tracking with assistance from stations like Deep Space Network facilities and collaboration with NASA's Jet Propulsion Laboratory. Thermal, power, and attitude control systems leveraged heritage from missions like Hiten and Nozomi, while avionics and deployment mechanisms reflected inputs from Mitsubishi Electric and academic laboratories.

Scientific Results and Discoveries

SELENE produced high-resolution digital elevation models and topographic maps that refined knowledge of lunar basins such as the Mare Imbrium, Oceanus Procellarum, and the far side's South Pole–Aitken basin. Multispectral data improved compositional maps identifying pyroxene- and olivine-rich terrains, complementing results from Clementine and Lunar Prospector. Gravity science from Doppler tracking and sub-satellite measurements yielded detailed gravity anomaly maps that constrained crustal thickness and mantle structure models, informing geophysical interpretations originally posed by studies at Caltech and Institut de Physique du Globe de Paris. The Lunar Radar Sounder detected subsurface layering and regolith structure, advancing understanding of volcanic and impact processes also studied by GRAIL and SMART-1. SELENE's plasma, charged particle, and exospheric sensors characterized interactions between the solar wind and lunar surface, relevant to research undertaken by Chandrayaan-1 and LADEE.

Operations and Mission End

Routine science operations continued for more than a year with data relayed through the sub-satellites and international ground networks including JAXA facilities and partner stations. After completing primary objectives and extended observations, mission controllers executed a controlled deorbit of the Main Orbiter, which impacted the lunar surface on 10 June 2009 in a planned termination similar in intent to terminations of Lunar Prospector and SMART-1. The sub-satellites ceased nominal science as planned prior to mission end; Okina and Ouna contributed crucial radio science and relay functions until their operations concluded.

Legacy and Impact on Lunar Exploration

SELENE's comprehensive datasets have been integrated into planetary archives used by researchers at institutions such as NASA's Ames Research Center, Smithsonian Institution, and academic centers globally, influencing subsequent mission design for Artemis program planning, commercial lunar ventures, and robotic precursors including Lunar Reconnaissance Orbiter follow-ons. The mission demonstrated Japanese capabilities in large-scale planetary missions, bolstering programs like Hayabusa2 and paving the way for future JAXA initiatives. SELENE's contributions to lunar cartography, gravity modeling, and subsurface science remain foundational for ongoing scientific investigations and exploration strategies by agencies including European Space Agency, Roscosmos, China National Space Administration, and Indian Space Research Organisation.

Category:Lunar exploration missions Category:Spacecraft launched in 2007