Artemis I – Flight Day Seven: Orion to Test Search Acquire and Track Mode, Exit Lunar Sphere of Influence
The R-4D-11 auxiliary engines are a variant of the flight-proven R-4D engine, which was originally developed for the Apollo program and was employed on every mission to the Moon. The engines are positioned at the bottom of the service module in four sets of two, and each provides about 100 pounds of thrust. In total, Orion’s highly capable service module has 33 engines of various sizes and serves as the powerhouse for the spacecraft. As such it provides the propulsion capabilities on its exploration missions which enable Orion to go around the Moon and back to Earth.
In the White Flight Control Room at NASA’s Johnson Space Center in Houston, the team continued testing the spacecraft’s star trackers to determine their sensitivity to thermal variations as part of planned testing. Engineers also used the optical navigation system to gather additional imagery of the Moon. The star trackers and optical navigation system are part of Orion’s advanced guidance, navigation, and control system, responsible for always knowing where the spacecraft is located in space, which way it’s pointed, and where it’s going. It even controls the propulsion system to keep the spacecraft on the correct path. The optical navigation can serve later in this mission and in future missions as a backup, ensuring a safe trip home should the spacecraft lose communications.
Earth rises from behind the Moon in this video captured by a camera on one of Orion’s solar array wings. The video was taken at 8:05 am EST on flight day six of the 25.5-day Artemis I mission, shortly after the outbound powered flyby and six minutes after the spacecraft regained connection with NASA’s Deep Space Network. Credit: NASA
Overnight, flight controllers will conduct the search acquire and track (SAT) mode developmental test objective. SAT mode is an algorithm intended to recover and maintain communications with Earth after the loss of Orion’s navigation state, extended loss of communications with Earth, or after a temporary power loss that causes Orion to reboot hardware. To test the algorithm, flight controllers will command the spacecraft to enter SAT mode, and after about 15 minutes, restore normal communications. Testing SAT mode will give engineers confidence it can be relied upon as the final option to fix a loss of communications when crew are aboard.
Orion will exit the lunar sphere of influence, or the gravitational pull of the Moon, at 10:31 pm CST and continue traveling toward distant retrograde orbit. The next live event will be NASA Television coverage of the distant retrograde orbit insertion burn, scheduled for 4:30 pm EST (1:30 pm PST) on Friday, November 25. Shortly before entering the orbit, Orion will travel about 57,287 miles ( 92.194 km) beyond the Moon at its farthest point from the lunar surface during the mission. View the Artemis I mission map (see image below) to see Orion’s path in space.
On Saturday, November 26, Orion will pass the record set by Apollo 13 for the farthest distance traveled by a spacecraft designed for humans at 248,655 miles (400,171 km) from Earth, and the spacecraft will reach its maximum distance from Earth of 268,552 miles ( 432,193 km) on Monday, November 28.
Just after 4 pm CST on November 22, Orion was traveling over 208,000 miles (335,000 km) from Earth and was over 36,000 miles (58,000 km) from the Moon, cruising at over 3,000 miles per hour (4,800 km per hour).
Listen to a replay of the Twitter Spaces NASA hosted Tuesday, November 22, with NASA Flight Director Gerry Griffin, Jim Geffre from Orion, Nijoud Merancy with the Artemis program and Jennifer Ross-Nazzal with the NASA history office to discuss the milestone.
Learn more about Orion’s systems that were designed for deep space missions with astronauts.