January 3 

 

3 January 1999


A Boeing Delta II 7425–9.5 launch vehicle lifts off with NASA's Mars Polar Lander from Launch Complex 17B, Cape Canaveral Air Station. Credit: NASA

The Mars Polar Lander and the attached two Deep Space 2 probes were launched at 20:21:10 UT, on January 3, 1999, on a Delta 7425 (a Delta II Lite launch vehicle with four strap-on solid-rocket boosters and a Star 48 (PAM-D) third stage) which placed them into a low-Earth parking orbit. The third stage fired for 88 seconds at 20:57 UT to put the spacecraft into a Mars transfer trajectory and the spacecraft and third stage separated at 21:03 UT.
 
   The spacecraft was part of the Mars Surveyor '98 program. It was to touch down on the southern polar layered terrain, between 73°S and 76°S, less than 1000 km from the south pole, near the edge of the carbon dioxide ice cap. The two penetrators, known as Deep Space 2, developed under the NASA New Millennium Program, were to impact the surface to test new technologies. All three probes crashed upon arrival at Mars on December 3, 1999.
 
The Mars Polar Lander is suspended from a crane in the Spacecraft Assembly and Encapsulation Facility-2 before being lowered to a workstand. Credit: NASA
  
   The mission had as its primary science objectives to: 1) record local meteorological conditions near the martian south pole, including temperature, pressure, humidity, wind, surface frost, ground ice evolution, ice fogs, haze, and suspended dust, 2) analyze samples of the polar deposits for volatiles, particularly water and carbon dioxide, 3) dig trenches and image the interior to look for seasonal layers and analyze soil samples for water, ice, hydrates, and other aqueously deposited minerals, 4) image the regional and immediate landing site surroundings for evidence of climate changes and seasonal cycles, and 5) obtain multi-spectral images of local regolith to determine soil types and composition.

   These goals were to be accomplished using a number of scientific instruments, including a Mars Volatiles and Climate Surveyor (MVACS) instrument package which was comprised of a robotic arm and attached camera, mast-mounted surface stereo imager and meteorology package, and a gas analyzer. In addition, a Mars Descent Imager (MARDI) was planned to capture regional views from parachute deployment at about 8 km altitude down to the landing. The Russian Space Agency provided a laser ranger (LIDAR) package for the lander, which would be used to measure dust and haze in the Martian atmosphere. A miniature microphone was also be on board to record sounds on Mars. Attached to the lander spacecraft were a pair of small probes, the Deep Space 2 Mars Microprobes, which were to be deployed to fall and penetrate beneath the martian surface when the spacecraft reached Mars. 

   The Mars Polar Lander consisted of a hexagonal base composed of aluminum honeycomb with composite graphite epoxy face sheets supported on three aluminum landing legs. The lander stood 1.06 m tall and approximately 3.6 m wide. The launch mass of the spacecraft was approximately 583 kg, including 64 kg of fuel, an 82 kg cruise stage, a 140 kg aeroshell/heatshield, and the two 3.5 kg microprobes. A thermally regulated interior component deck held temperature sensitive electronic components and batteries and the thermal control system. Two solar panels extended out from opposite sides of the base. Mounted on top of the base were the robotic arm, the stereo imager and mast, a UHF antenna, the LIDAR, the MVACS electronics, the meteorology mast and the medium gain dish antenna. The MARDI was mounted at the base of the lander, and the propellant tanks were affixed to the sides. During cruise, the lander was attached to the cruise stage and enclosed in the 2.4 meter diameter aeroshell.
 
Artist's depiction of the Mars Polar Lander on the Martian surface, as it would appear if it landed successfully. Credit: NASA / JPL

See also: Mars Climate Orbiter

References:

Asif A. Siddiqi. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. Washington, DC: NASA History Program Office, 2018. ISBN 978-1-62683-042-4
© 2026, Andrew Mirecki 
 

 

3 January 2019 

 
Chang'e 4 lander with the ramp designed for Yutu 2 rover deployment. Photo taken by the rover. 
Credit: CNSA/Siyu Zhang/Kevin M. Gill

Chinese Chang'e 4 spacecraft with Yutu 2 lunar rover successfully landed in the Von Kármán crater in the South Pole-Aitken Basin at 02:26 UTC on January 3, 2019, becoming the first spacecraft to make a controlled landing on the far side of the Moon. Landing coordinates were calculated within a few meters from LRO images as 45.4561° S, 177.5885° E. 

   The Chang'e 4 probe began its soft landing on January 3, 2019. The communication link between the probe and relay satellite became active at 01:34 UTC, and the probe entered the far-side orbit at 01:41. The 7500 N engine started working at 02:14, entering the primary deceleration phase and starting the powered descent. Then, it sequentially performed the approaching descent at 02:23, hovering at 02:25, and obstacle avoidance at 02:25. Finally, the Chang'e 4 probe successfully landed on the surface of the Moon at 02:26:02. The whole powered descent process lasted 687 s.
 
Photo taken during the landing maneuver. Credit: CNSA
 
   The Yutu 2 rover was driven down ramps onto the surface about 12 hours later, at 14:22 UT. The rover moved forwards towards a small crater and turned on its instruments. On 6 January 6, the rover went into a planned hibernation to protect itself from the heat of lunar noon and reawoke on January 10, and continued travelling and making measurements. The rover shut down over the local lunar night, beginning about January 13-14. Both the lander and rover used a radioisotopic heat source to maintain survival temperatures. Yutu 2 resumed daytime operations on January 29, and the lander a day later. It has been hibernating during the lunar night and operational during the day, as planned. Launched on December 7, 2018, the lander and the rover were still operating as of October 2022. 
 
Yutu-2 rover on lunar surface. Credit: CNSA

   The lander has a dry mass of 1200 kg, carrying its own experiments and the rover. The experiments include a low-frequency (0.1 - 40 MHz) radio spectrometer (LFS), a Landing Camera (LCAM), Terrain Camera (TCAM), a Lunar Lander Neutrons and Dosimetry Experiment (LND), and a biological experiment.

   It includes a rover, Yutu 2, based on the Chang'e 3 Yutu rover. The rover, with a total mass of 140 kg, has a rectangular body 1.1 meters high, 1.5 m long, and 1 m wide, but unlike the Chang'e-3 rover it has not  a robotic arm. It has 6 wheels, two solar panels, and a dish antenna. Its scientific payload comprises cameras, including a Panoramic Camera (PCAM), a Visible/Near-Infrared Imaging Spectrometer (VNIS), Lunar Penetrating Radar (LPR), and the Advanced Small Analyzer for Neutrals (ASAN). 
 
   Chang'e 4 used a communication relay satellite, in a halo orbit around the Earth-Moon L2 point to maintain communication between the lander and Earth ground control. The satellite, Queqiao, based on the Chang'e 2 design, was launched on May 20, 2018, to enable communication with the far side of the Moon. 
 
Yutu 2, casting a shadow, looks back toward the Chang'e 4 lander in July 2019. Image processed by Doug Ellison. Credit: CNSA/CLEP/Doug Ellison


A view of landing site, marked by two small arrows, on the floor of Von Kármán crater, taken by the Lunar Reconnaissance Orbiter on 30 January 2019. Credit: NASA/GSFC/Arizona State University

Chang'e 4 landing sequence on YouTube


References:

Liu, J., Ren, X., Yan, W. et al. Descent trajectory reconstruction and landing site positioning of Chang’E-4 on the lunar farside. Nat Commun 10, 4229 (2019). https://doi.org/10.1038/s41467-019-12278-3
Li, C., Zuo, W., Wen, W. et al. Overview of the Chang’e-4 Mission: Opening the Frontier of Scientific Exploration of the Lunar Far Side. Space Sci Rev 217, 35 (2021). https://doi.org/10.1007/s11214-021-00793-z


See also: Chang'e 1, Chang'e 2, Chang'e 3, Chang'e 5, Chang'e 6


 © 2026, Andrew Mirecki
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