Chang′e 4

Launch data:

Description:

• Chang′e 4 is expected to touch down in Von Kármán Crater, within the SPA basin.
  The mission, aims to complete:
  • A low-frequency radio-astronomical study on the lunar surface;
  • A shallow-structure investigation at the lunar far side within the roving area;
  • Topographic and mineralogical composition studies of the lunar far side within the rover's patrol area.
• The radio-astronomical study is particularly intriguing. The lunar far side always faces away from Earth, so it′s is free from interference from our planet′s ionosphere, human-made radio frequencies and auroral radiation noise. Solar radio emission is also blocked during the lunar night.
• The Chang′e-4 mission is part of the second phase of China′s lunar program, which includes orbiting, landing and returning to Earth. It follows the success of the Chang′e-1, Chang′e-2 and Chang′e-3 missions in 2007, 2010 and 2013.
• The launch mass of Chang′e-4 spacecraft is around 3,780 kg, while the lander has a mass of around 1,200 kg and the rover has a mass of 140 kg.
  The mission is composed of two distinct elements: the lander and the rover. The lander is equipped with a radioisotope thermoelectric generator (RTG) to power the lunar operations during the three-month mission. The energy will be used to power the scientific payload of seven instruments and cameras.
  The lunar rover will explore the lunar surface after departing the lander and is equipped with a solar panel to power the vehicle during the lunar day on a three month mission.
  
  

  Change 4 lander on the moon.

  Change 4 rover on the moon on.

  
  
• The lander carries the Landing Camera (LCAM), the Terrain Camera (TCAM), and the Low Frequency Spectrometer (LFS).
  There are also three international joint collaboration payloads installed on the Chang′e-4 explorer, which are the Lunar Lander Neutrons and Dosimetry (LND) installed on the lander and developed in Germany, the Advanced Small Analyzer for Neutrals (ASAN) installed on the rover for observations of energy-neutral atoms and positive ions in patrol area to investigate the particle radiation environment in the patrol area, and the Netherlands-China Low-Frequency Explorer (NCLE) installed on the relay satellite Queqiao.
  The LFS is newly developed for Chang′e-4 lander, and another five kinds of payloads are the inherited instruments from Chang′e-3.
  The LFS will be used for the detection of low-frequency radio frequency characteristics of the sun and the moon′s low-frequency radio environment to perform low-frequency radio astronomy observations.
  The LFS is used for detecting the low-frequency electric field of the solar storm and to study the Lunar plasma. By detecting the low-frequency electric field from the Sun, the planetary space and the galactic space, the information of electric magnitude, phase, time variance, frequency spectrum, polarization and DoA (Direction of Arrivals) are collected for analysis. With features of variation of the spatial low-frequency electric field, the Lunar plasma environment above the landing site will be analyzed.
• The LFS is configured with a three-component decomposition active antenna to receive electromagnetic signals from the Sun and from space.
  Each of the three antenna units receives one of the three orthogonal components of the electromagnetic signals. According to radio transmission theory, information such as the electromagnetic intensity, the frequency spectrum, the time variance, the polarization features and the direction of radiation source are obtained by analyzing and processing the exploration data.
• The LCAM landing camera will be used for optical imaging of the landing area during descent to investigate surface morphology and geological structure, while the objective of the TCAM terrain camera will be for optical imaging of the landing area to investigate surface morphology and geological structure.
• The LND was developed by the Christian-Albrechts-University in Kiel (CAU), Germany, with contributions from the Institute for Aerospace Medicine of the German Space Center, the National Space Science Center (NSSC), the National Astronomical Observatories (NAOC) from the Chinese Academy of Sciences (CAS), and the China Academy of Space Technology (CAST). LND is supported by DLR (German Space Agency) through the Federal Ministry of Economics and Technology.
  The LND instrument will be accommodated on the Chang′e-4 Lander and has two major science objectives to dosimetry for human exploration of the Moon and to contribute to heliospheric science as an additional measuring point.
  LND is designed to measure the time series of dose rate and of linear energy transfer (LET) spectra in the complex radiation field of the lunar surface.
• Biological Payload
  • Asides from the aforementioned physical experiments, the lander will carry a small 3kg package containing silk worm eggs and some seeds from the Arabidopsis Thaliana (thale cress) plant as well as potato seeds.
  • The experiment, designed by 28 Chinese university students, will effectively serve as a mini-biosphere in which the samples will (hopefully) thrive, and with a bit of luck will provide a closed-loop environment in which the specimens will form a symbiotic relationship.

Mission details:

• China launched its fourth and most ambitious lunar exploration mission on Dec 7, 2018. Liftoff of the Chang′e-4 probe with latest lunar rover took place at 18:24 UTC from the Xichang Satellite Launch Center using a Long March-3B/G3Z launch vehicle thundering from the LC2 Launch Complex. If successful, this will be the first mission to land on the far side of the Moon.
  The launch took place on the first opportunity of the launch window available from 18:15 UTC to 18:34 UTC.
  
• The Chang′e-4 was launched into a 200 x 420000 km x 29.4 deg orbit. The vehicle is similar in design to Chang′e-3 and carries a 140 kg lunar rover similar to that mission′s Yutu.
  It is scheduled to enter lunar orbit on Dec 11 at about 1500 UTC and land in the farside South Pole-Aitken region on about Jan 4.
  
• Due to the difficulty in communicating with the far side of the Moon, the Chinese National Space Agency (CNSA) has been making use of a relay satellite Queqia, located at the L2 Earth-Moon LaGrange point. The satellite will relay communications from the lander and rover to Earth.
  The communications link is a critical part of the mission architecture, so it′s worth making sure everything works. There are no second chances on a mission like this!
• The CZ-3B Y30 third stage, in a similar initial orbit of about 200 x 390000 km, will fly past the lunar surface at a height of 4840 km around 1138 UTC Dec 12, 2018 and end up in a 181000 x 735800 km x 23.6 deg orbit, according to calculations based on observations at Haleakala.
• Chang′e-4 completed its lunar orbit insertion burn at 0845 UTC Dec 12, 2018; China reported the vehicle is in a 100 x 400 km orbit, presumably polar.
  Radio tracking by S. Tilley and others derive a 138 x 445 km x 85.0 deg orbit. On Dec 30 at 0054, the orbit was lowered to 15 x 100 km.
• At 0214 UTC on Jan 3, 2019 Chang′e-4 began its descent burn from lunar orbit, and it landed in Von Karman crater at 177.59E 45.46S at 02:26 UTC Jan 3.
  At 14:22 UTC the same day, the Yutu-2 rover rolled onto the surface and began its explorations of the area.
  
  

  Image taken after the soft landing, courtesy of CNSA.

  First surface image from the far side (Image credit: CNSA)

  
  

  Close-up of Biosphere canister on Earth (Image credit: CNSA/Chongqing University).

  Life begins! The cotton seed sprouting on the Moon (Image credit CNSA/Chongquing University)

  
  

External links:

• SpacetechAsia: China′s seeds sprouted on the Moon. (Credit: #167)
• SpacetechAsia: Launch, payload and landing zone. (Credit: #167)
• Diligentias.com: Chang´e Landing
• EOportal.org Satellite and mission description
• The Guardian: What could Chang′e 4 discover on far side of the moon?
• Satellite tracking: Real time satellite tracking

Astrophilately covers:

Credit: J. Esders