How does one confirm that a crewed spacecraft, swinging far outside of Earth’s low orbit, is in fact where you say it is? Part of the answer came from the same machine used to look at stars and galaxies, in the form of NASA’s Artemis 2 mission. For five days straight, a telescope funded by the National Science Foundation located in West Virginia watched Orion swing through its close approach of the Moon, giving another precision point on the spacecraft’s journey when carrying four astronauts past 200,000 miles from Earth.
The picture it took of Orion is not a very pretty one. But it contains a striking element. “There are four people in those pixels,” according to a Green Bank Observatory scientist, Will Armentrout. At the time when this telescope captured this image of the spacecraft, Orion called Integrity by its crew was more than 213,000 miles away from the planet we call home.
The technical meaning of the accomplishment goes much further. As explained by the observatory’s director Anthony Remijan: “Green Bank’s telescope tracked Orion’s motions to within 0.2 millimeters per second compared to NASA’s projections.”It’s like having a speedometer in your car that can track your speed within 0.0004 decimal places per hour.”
That is to say that independent confirmation that a spaceship is on its course becomes particularly valuable for deep space missions, where relying on the spacecraft to confirm its own location is just one option. More importantly, that kind of measurement can give the teams additional tools to navigate a spaceship in addition to what is carried aboard the spaceship.
It also stands out from the general work done by any ground facility supporting space missions. While a number of sites around the world will simply listen for the signals sent from a spaceship, in the case of Artemis 2 the telescope actively measured the position of the ship by coordinating with other NASA assets. This meant that a radio telescope in California fired pulses of radio waves towards Orion, and 100-meter dish of Green Bank picked up its weak echo.
There are other implications for future space exploration. First of all, it means that there are options for ground-based facilities that are independent of the existing global network of Deep Space Network antennas, and yet can still provide useful data about spacecrafts’ motion. Second of all, it gives another dimension of verification of spacecraft’s state beyond listening to it.
In particular, NASA is already opening up real-time tracking of missions such as Orion’s through a special website that provides information based on the ship’s data. At the same time, ground-based telescopes such as Green Bank are already involved in similar projects and can be relied upon to verify spacecraft’s location independently from it. In addition, Green Bank and other observatories have already been involved in missions such as DART and have supported lunar landers with their National Radio Astronomy Observatory facilities. With Artemis 2 mission, Green Bank’s contributions become widely recognized.