Lunokhod 1

Spacecraft and rover design

The Luna 17 spacecraft soft-landed on the Moon and served as the deployment platform for the rover. It was equipped with dual descent ramps so that Lunokhod 1 could egress from either side, providing redundancy in the event of obstacles near the lander.

Lunokhod 1's body consisted of a tub-like pressurised compartment topped by a large convex hinged lid that bore the solar array panels. The rover measured approximately 2.15 m in length and 1.35 m in height, with a wheelbase of about 1.6 m. It rode on eight independently powered wheels, each with its own drive motor, giving it the ability to continue moving even if individual motors failed.

Two antenna types provided the communications link with Earth: a low-gain cone-shaped omnidirectional antenna for general contact, and a highly directional helical antenna for higher-bandwidth transmissions routed through Soviet deep-space tracking stations.

Four television cameras were mounted on the rover — a front-mounted stereo pair to assist remote driving, plus additional cameras for navigation and panoramic imaging. Combined, they returned more than 20,000 TV images and approximately 200–206 panoramas across the mission.

Power and thermal control

During the lunar day, the hinged lid was tilted to maximise solar-panel exposure, generating approximately 180 W of electrical power that drove the motors and charged onboard rechargeable batteries. When a lunar night began — plunging temperatures to around −150 °C — the lid was closed and the rover entered a hibernation state.

Thermal survival through the roughly 14-Earth-day lunar night was provided by a polonium-210 radioisotope heater unit (RHU), which kept the internal electronics above their minimum operating temperature without requiring any external power source. At the next lunar sunrise, controllers re-established contact and resumed traverses.

Rediscovery in 2010

When Lunokhod 1 fell silent in September 1971, its precise final location was not well constrained, and subsequent attempts to obtain a laser return from its retroreflector were unsuccessful. The rover's position remained uncertain at the kilometre scale for nearly four decades.

On 17 March 2010, Albert Abdrakhimov identified both the Luna 17 lander and the Lunokhod 1 rover in a Lunar Reconnaissance Orbiter Narrow Angle Camera image (M114185541RC). The LRO Camera team, led by Mark Robinson at Arizona State University, derived coordinates accurate to roughly 100 m by combining the high-resolution imagery with altimetry from the Lunar Orbiter Laser Altimeter.

Using those coordinates, the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) team, led by Tom Murphy of UC San Diego, aimed the observatory's 3.5 m telescope at the site on 22 April 2010. A strong return signal was detected immediately, confirming the rover's location. The initial measurement placed the reflector approximately 40 m offset in range — about 100 m laterally — from the LRO-based estimate, at the edge of APOLLO's timing gate.

By combining ranging measurements taken at different lunar librations, the APOLLO team intersected the resulting distance spheres to triangulate the reflector's position. By November 2010 the coordinates were known to within about one centimetre. The retroreflector was found to be in excellent condition, returning a signal roughly four times stronger than that from Lunokhod 2's reflector. The results were published in the 2011 paper "Laser ranging to the lost Lunokhod 1 reflector" in Icarus. Because the site lies near the lunar limb as seen from Earth, Lunokhod 1's reflector is particularly valuable for constraining lunar libration and the orientation of the Moon.