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Lost Moon orbiter found using new radar technique

Goldstone Deep Space Communications Complex

DSS-14, NASA’s 230-foot (70-meter) antenna at the Goldstone Deep Space Communications Complex in California. Photo Credit: NASA / JPL-Caltech

NASA has spotted a lost spacecraft orbiting the Moon as well as its own Lunar Reconnaissance Orbiter thanks to a newly developed radar technique.

The lost spacecraft was the Indian Space Research Organization (ISRO) Chandrayaan-1 spacecraft, which ceased operations in 2009. The new technique employs the use of interplanetary radar and was developed by scientists at NASA’s Jet Propulsion Laboratory (JPL).

By using the technique to detect the locations of one active and one dormant spacecraft, scientists are pioneering a technique that could be used to assist planners for future Moon missions.


Radar imagery acquired of Chandrayaan-1 as it flew over the lunar south pole on July 3, 2016. The imagery was acquired by the Goldstone Deep Space Communications Complex in California. Caption and Image Credit: NASA / JPL-Caltech

“We have been able to detect NASA’s Lunar Reconnaissance Orbiter [LRO] and the Indian Space Research Organization’s Chandrayaan-1 spacecraft in lunar orbit with ground-based radar,” said Marina Brozovic, a radar scientist at JPL and principal investigator for the test project. “Finding LRO was relatively easy, as we were working with the mission’s navigators and had precise orbit data where it was located. Finding India’s Chandrayaan-1 required a bit more detective work because the last contact with the spacecraft was in August of 2009.”

The new technique employed the use of the 230-foot (70-meter) antenna at NASA’s Goldstone Deep Space Communications Complex in California and the 330-foot (100-meter) Green Bank Telescope in West Virginia.

During the experiment, the team directed the Goldstone antenna to transmit a powerful beam of microwaves toward the Moon and used the Green Bank Telescope to receive the radar echoes that returned back to Earth.

When compared to LRO, Chandrayaan-1 is very small, measuring about 5 feet (1.5 meters) on each side. However, Chandrayaan-1 remained in a polar orbit around the Moon, which, according to JPL, made it a perfect target to demonstrate the new radar technique.

On July 2, 2016, the JPL team pointed the Goldstone antenna to just above the Moon’s north pole and waited for the spacecraft to cross in front of the radar beam.

Based on orbital parameters from 2009, Chandrayaan-1 was predicted to be completing an orbit around every 2 hours and 8 minutes. During 4 hours of observation, scientists observed the radar signature of a small spacecraft twice during the period, which corresponded with Chandrayaan-1. The radar data was used to calculate the spacecraft’s distance and velocity in order to improve future predictions for its orbit.

“It turns out that we needed to shift the location of Chandrayaan-1 by about 180 degrees, or half a cycle from the old orbital estimates from 2009,” said Ryan Park, the manager of JPL’s Solar System Dynamics group, who delivered the new orbit back to the radar team. “But otherwise, Chandrayaan-1’s orbit still had the shape and alignment that we expected.”

By observing LRO and rediscovering Chandrayaan-1 using the new radar technique, scientists are demonstrating that ground-based radars can be used on future missions to the Moon to aid in collision avoidance and to assist with spacecraft that encounter navigation or communication issues.


A depiction of the orbit of Chandrayaan-1’s orbit at the time it was detected by Goldstone. The 120-mile (200-kilometer) wide purple circle represents the width of the Goldstone radar beam at lunar distance while the white box in the upper-right corner depicts the strength of the radar echo. Caption and Image Credit: NASA / JPL-Caltech




Paul is currently a graduate student in Space and Planetary Sciences at the University of Akransas in Fayetteville. He grew up in the Kansas City area and developed an interest in space at a young age at the start of the twin Mars Exploration Rover missions in 2003. He began his studies in aerospace engineering before switching over to geology at Wichita State University where he earned a Bachelor of Science in 2013. After working as an environmental geologist for a civil engineering firm, he began his graduate studies in 2016 and is actively working towards a PhD that will focus on the surficial processes of Mars. He also participated in a 2-week simluation at The Mars Society's Mars Desert Research Station in 2014 and remains involved in analogue mission studies today. Paul has been interested in science outreach and communication over the years which in the past included maintaining a personal blog on space exploration from high school through his undergraduate career and in recent years he has given talks at schools and other organizations over the topics of geology and space. He is excited to bring his experience as a geologist and scientist to the Spaceflight Insider team writing primarily on space science topics.

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