At 10:15 am Eastern time Thursday, the engineering teams of SpaceIL and Israel Aerospace Industries (IAI) will perform the most critical maneuver yet in the historic journey of Israel’s first spacecraft to travel beyond Earth’s orbit — Beresheet – now on its way to the moon.
Lunar orbit insertion, or “Lunar Capture” as the maneuver is called, allows the spacecraft to enter the moon’s gravity and begin orbiting prior to landing.
Up to this point, Beresheet has been circling the Earth in elliptical orbits, and performed seven maneuvers to send it higher and further away.
Earlier this week, Beresheet passed its closest point to Earth for the last time at 1,700 kilometers (1,056 miles), and then continued to its meeting point with the moon at a range of 400,000 kilometers (248,548 miles).
Unlike the maneuvers Beresheet has performed so far, when its engines were operated to accelerate the spacecraft, the current engine operation is meant to SLOW the spacecraft’s velocity, so that it is captured by lunar gravity. The braking will reduce Beresheet’s velocity relative to the moon from 8,500 km/h (5,281 mph) to 7,500 km/h (4,660 mph).
If the slowdown does not take place as planned, the spacecraft risks leaving Earth’s gravity while missing the moon’s gravity and will enter a different and undesirable orbit in the solar system. This would bring the mission to an end.
A successful maneuver will position the spacecraft on an elliptical orbit around the moon, in which the nearest point (perilune) is 500 km (310 miles) away from the moon, while the farthest one (apolune) is 10,000 km (6,213 miles) away.
In the week following the capture, the SpaceIl and IAI teams will perform several maneuvers to reduce the orbits around the moon from an elliptical to a round orbit 200 km (124 miles) above the moon.
Unlike the long Earth orbits, the first lunar orbits will last 14 hours. As Beresheet approaches landing, each moon orbit will last only two hours. These maneuvers are meant to lower the spacecraft’s altitude and reach the optimal point for autonomous landing in the moon’s Sea of Serenity the evening of April 11.
Thus far, the spacecraft has traveled 5.5 million kilometers (more than 3.4 million miles) in its orbits. It will travel one million more while orbiting the moon. Beresheet has used 80 kilograms (176 pounds) of fuel so far.
The spacecraft has also experienced two challenges both of which the engineering team was able to overcome: one with its star trackers which were more blinded by the sun than originally expected, and the other involving undesirable re-starts of the mission computer.
Beresheet was launched on February 22 at 3:45 a.m. Israel time (8:45 p.m. local time) from Cape Canaveral, Florida, on a SpaceX Launchpad by a Falcon 9 rocket as secondary payload alongside two satellites. The first data from the spacecraft was received by 4:23 a.m. and at 4:25 a.m. Israel time, when Beresheet deployed its landing legs as planned.
Once it lands on the moon, the spacecraft carrying the Israeli flag will begin taking photographs of the landing site and a selfie to prove Israel landed on the moon.
Beresheet has an important scientific mission to complete: to measure the moon’s magnetic field as part of an experiment carried out in collaboration with the Weizmann Institute of Science in Israel.
NASA is also participating in the mission under an agreement entered with the Israel Space Agency. NASA has installed a laser retro-reflector on the spacecraft and will assist in communicating the spacecraft on the moon.
The spacecraft carries a time capsule it will place on the moon, with hundreds of digital files ranging from details about SpaceIL, the spacecraft and the crew of the project, national symbols, cultural items and materials collected from the general public over the years. Since the spacecraft is not expected to return to Earth, the information it carries is destined to remain on the moon for an indefinite period and may be found and distributed by future generations.
IAI has been a full partner in the project since its inception, with additional partners added over the years from the private sector, government and academia. Among the main contributors to the project are Dr. Miriam and Sheldon Adelson, Sammy Sagol, Lynn Schusterman, Sylvan Adams, Stephen Grand and others, in addition to the Weizmann Institute of Science, the Israeli Space Agendy, the Ministry of Science and Technology, and Israeli telecommunications firm Bezeq. Philanthropist and businessman Morris Kahn took the lead in completing the mission by funding $40 million of the project, and in his role as president of SpaceIL