SELENE

Kaguya (Japaneseかぐや), project name SELENE ( selenological and Engineering Explorer at the same time the Greek name of the moon and the Greek moon goddess Selene ), was a lunar orbiter of the Japanese space agency JAXA. The mission was named after the moon princess in the Japanese legend Taketori Monogatari. JAXA refers to the spacecraft as "The large largest lunar mission since the Apollo program" (the largest lunar mission since the Apollo program ). The launch of Kaguya took place on 14 September 2007 from the Tanegashima Space Center aboard an H-IIA rocket.

Mission Objectives

The primary objectives of the mission include the study of the mineralogical composition of the moon, the topography, geology, gravity field and the plasma in the Moon and the Sun-Earth system. In addition, the probe is designed to test technologies that are critical for future lunar missions.

Technology

The mission consists of three satellites: a large orbiter, which carries most of the scientific payload, a VLBI Radio Satellite ( VRAD ) and a relay satellite, the communication of the earth with the main orbiter during flight phases in which it is located behind the moon, serves.

Orbiter

The main orbiter has a rectangular shape and is about 2.1 × 2.1 × 4.2 m tall. It is divided into two parts: The 2.8 m long upper mission module that contains the most scientific instruments, and detachable 1.2 m long lower drive module. A single solar panel located on one side of the spacecraft. 1.3 m high-gain antenna is at 90 ° angle to the solar panel is attached to another side of the probe. A 12 m long magnetometer boom extends out from the front of the probe, an additional four 15 m long radar antennas are mounted on the corners of the mission module. The total unladen weight of the probe is 1720 kg. In addition, 795 kg of fuel are taken.

Power is supplied by the solar panel, which consists of 22 m2 GaAs / Ge solar cells that can generate up to 3486 W of power. The solar panels feed four NiH2 batteries with a capacity of 35 Ah, provide a voltage of 50 volts. Communication is via the high-gain antenna in the S- and X-band. The data rate over the X-band is up to 10 Mbit / s to 60 m large bowl and S-band ( 2263.6 MHz ) to 2 kbit / s to 40 m large bowl. Four non-directional S-band antennas are / used to transmit commands to the probe at a rate of 1 kbit s. The storage capacity of the onboard storage system is 10 GB.

The main engine of the probe is located in the drive module. It provides a thrust of 500 N and burns NTO and hydrazine. At the end of the mission, the module will attempt a soft landing on the moon. The mission modules carries 13 scientific instruments: a multi-band camera, a terrain camera, a TV camera, a spectral profiler, an X-ray spectrometer, a gamma-ray spectrometer, a radar, a laser altimeter, a magnetometer, a plasma imager, a spectrometer for charged particles, a plasma analyzer and equipment for radio experiments.

On the outer shell of the probe two plates were attached, on which the name and sent messages have been engraved by over 410,000 people.

Subsatellites

The two sub-satellites of Kaguya are very similar in structure. Everyone has an octagonal cylindrical shape and measures 1.0 x 1.0 x 0.65 m with a mass of 50 kg. Both satellites have a dipole antenna, are spin-stabilized with ten revolutions per minute and who have no engines. The energy is supplied by solar cells that are mounted on the sides of the satellites. These provide 70 W of power and feed each a 26 V NiMH battery pack with a capacity of 13 Ah.

VRAD satellite ( Ouna )

The satellite has an X-band and three S-band radio sources. He, in conjunction with the relay satellite ground-based differential VLBI measurements ( Very Long Baseline Interferometry ). The satellite was suspended on 12 October 2007 in a polar orbit between 100 km and 800 km altitude and should be able to survive long in orbit over a year.

Relay satellite ( Okina )

The relay satellite also has a X-band and three S-band radio sources and is used to route the signal between the orbiter and the Earth, which on the side of the moon is necessary in the measurements of the gravity field. The satellite was exposed on 9 October 2007 in an orbit with a periapsis of 100 km and an apoapsis of 2400 km and should be able to survive long in orbit over a year. The relay satellite slapped on the moon back on 12 February 2009 at 19:46 clock ( JST).

Mission

The originally planned for late 2005 launch of the Kaguya mission was moved in late 2003 to August 2006 due to the launch failure of the sixth H -2A rocket. Later the start moved further into the year 2007. A scheduled for August 16, 2007 date had to be postponed to September 13 due to faulty capacitors built into the sub-satellites. Bad weather forced the JAXA, again to postpone the start by 24 hours.

Kaguya was launched on 14 September 2007 at 1:31 UTC of an H -2A rocket from Tanegashima Space Center into a 270 km high parking orbit around the Earth with an inclination of 30.4 ° ​​. Then the probe was sent on a journey to the moon.

On 29 September, for the first time succeeded in recording a sequence of images of the Earth in high definition picture quality. The photos show the Earth from 110,000 km away.

After two course corrections Kaguya reached on 3 October 2007 and entered the moon at 21:20 UTC into a polar lunar orbit between 101 km and 11,471 km height. The probe took 16 hours and 42 minutes for one round.

On 9 October at 00:36 UTC Kaguya put the relay satellite rstar in a lunar orbit, which is between 100 km and 2400 km above the lunar surface. Three days later, the VRAD satellite, whose orbit extends lower.

As planned, the orbiter went into its polar orbit target with a two-hour turnaround time on 19 October 2007. After the lowering of the apoapsis orbital altitude is between 80 km and 123 km above the lunar surface. This orbit is to be retained for one year, of which about every two months orbit corrections take place. Two days later, Kaguya was transferred to the operational mode and begin with the system check.

During the test phase of the HDTV camera from Ikegami took the orbiter on October 31, two more minute films on in high-definition quality. It was the first HDTV images, which were made from the lunar surface.

The test phase of all onboard systems was completed in two months and Kaguya took on 21 December 2007 his scientific work on. Work According to the JAXA the X-ray and the Ladungsteilchenspektrometer (CPS ) is not yet at full capacity. The former is made of four individual cameras can be connected together in order to achieve a higher resolution. During the review showed the simultaneous operation too high a noise. When CPS there had been overheating when the device was switched on for longer than two hours.

Kaguya struck on 10 June 2009 at 20:25 CEST at 80.4 ° ​​E, 65.5 ° S ( near the crater Gill) with about 6000 km / h on the lunar surface, and thus ended his mission. The impact and the resulting dust raised could be observed with ground-based telescopes. The evaluation of the data obtained by Kaguya will take some years to complete.

Scientific Results

The mission provided detailed three-dimensional topographic images of the lunar surface and a measurement of the gravitational field and the far side of the moon. Kaguya also provided the first optical images of the interior of the crater Shackleton at the South Pole, but it was not as hoped there evidence of water ice.

A map of the lunar surface for distribution of uranium, thorium and potassium could not be created until 31 October 2008 on the basis of measurements of the gamma-ray spectrometer (GRS) of 14 December 2007 to 17 February 2008 and 7 July.