Leonard David's INSIDE OUTER SPACE

Impact zone of the Chang’e 5-TI booster, expected to slam into the northern end of Hertzsprung crater, a large impact crater on the far side of the Moon.
Credit: NASA/LROC/ASU/Scott Sutherland

The time grows closer for that wayward rocket stage to bombard the Moon and the March 4 impact on the Moon’s far side has earned scientific attention.

The Goldstone Solar System Radar near Barstow, California was set to observe the object a few days before impact.

But the radar track had to be cancelled on March 1, one day before the planned track yesterday, due to an equipment problem affecting a powerful transmitter at the site, said Jon Giorgini, an engineer at NASA’s Jet Propulsion Laboratory.

“It is still being worked and I’m told there is no chance rescheduling a track prior to the March 4 impact,” Giorgini said.

Meanwhile, NASA’s Lunar Reconnaissance Orbiter (LRO) will be used to look for burps in the Moon’s exosphere — a very thin layer of gases — due to the crash and then later scan the lunar surface for the impact crater itself.

“LRO is ready for the impact, the tracking from last week gave us slight updates to timing and a range of predicted impact points,” observes Noah Petro, Project Scientist for the LRO at NASA Goddard Space Flight Center. “We’re ready! It may be some time for the data to be analyzed to see what we detect, if anything,” he points out.

Then LRO will set about to spot the crater, starting about a month from now when the spacecraft passes over the site in daylight, Petro adds.

At the ready! NASA’s Lunar Reconnaissance Orbiter (LRO).
Credit: NASA/GSFC

The discarded rocket booster is on track to slam into Hertzsprung Crater on the far side of the Moon, the first known piece of litter to inadvertently smack into the lunar surface.

Booster identified

Originally, the booster was thought to be part of a SpaceX Falcon 9 rocket that launched the National Oceanic and Atmospheric Administration’s Deep Space Climate Observatory in 2015.

However, the object is now tied to a Chinese Long March 3C rocket that blasted off in 2014.

Tagging the out-of-control stage to China comes from Bill Gray, manager of Project Pluto that supplies astronomical software, both commercial and freeware, to amateur and professional astronomers.

Following a circumlunar voyage in 2014, a return capsule parachuted to Earth. This test was a prelude to China’s Chang’e-5 lunar mission.
Courtesy: China Space

“There really is no good reason at this point to think the object is anything other than the Chang’e 5-T1 booster,” Gray told Inside Outer Space earlier. “Anybody claiming otherwise has a pretty large hill of evidence to overcome.”

That Chinese booster tossed an experimental spacecraft tagged as Chang’e-5-T1 that looped behind the Moon and returned to Earth to test atmospheric re-entry capabilities for 2020’s Chang’e-5 lunar sample return mission.

Chang’e-5-T1 also carried a secondary payload of scientific instruments in the upper stage of the Long March rocket on behalf of the Luxembourg-based company LuxSpace.

The LuxSpace 4M mission was dedicated to the late Manfred Fuchs. 4M stands for the Manfred Memorial Moon Mission.
Credit: OHB/LuxSpace

Cratering process

This event will be similar to the Apollo Saturn SIVB impacts in the past, in that the projectile is more or less a tin can, explains Jeffrey Plescia, a planetary scientist at the Johns Hopkins University’s Applied Physics Laboratory. “The result is that a lot of the energy goes into crushing the projectile rather than excavating the crater,” he tells Inside Outer Space.

The SIVB stages, as well as U.S. Ranger Moon probe craters are shallower than a normal crater and typically have an asymmetric shape, related for the most part to the low impact angle, Plescia adds. “Always good to know the parameters of the projectile for better understanding the cratering process.”

The crater in the center of this image was formed by Apollo 14’s Saturn IVB booster, intentionally impacted into the lunar surface on Feb. 4, 1971. The impact caused a minor “moonquake” that scientists used to learn about the Moon’s interior structure. Seismometers placed earlier on the surface by Apollo astronauts returned data on the tremor.
Credits: NASA/Goddard Space Flight Center/Arizona State University

Plescia notes that the impact event can be more reliably measured – such as depth of the resulting crater — as pre-impact images have been taken by LRO’s powerful camera system of the crash site.

“The only uncertainty at the moment is the orientation of the booster with respect to the trajectory. It is spinning but whether it is just turning in rotisserie mode or tumbling is not clear,” Plescia says. “I would hope the Chinese actually know this and would be forthcoming.”

Paint of a different stripe

Enter Vishnu Reddy and his student researchers at the University of Arizona in Tucson that have made observations of the errant upper stage.

Reddy and his team observed the Moon impactor on February 7, obtaining a spectrum of the object. They utilized the Rapid Astronomical Pointing Telescopes for Optical Reflectance Spectroscopy (RAPTORS) system, a telescope atop the Kuiper Space Sciences building on campus.

Credit: University of Arizona

“Then we compared its spectrum to those of a Falcon 9 2nd stage booster of similar provenance as the DSCOVR mission and a Chinese booster of similar provenance as the Chang’e 5 T-1 mission,” Reddy explains. The differences in spectrum were chiefly due to the type of paint used by the Chinese contrasted to SpaceX.

Vishnu Reddy (second from left) and his student researchers at the University of Arizona with RAPTORS system.
Credit: Mikayla Mace Kelley, University Communications/University of Arizona

“Both these boosters were in Earth orbit and were launched around the same year as the Chang’e 5 T-1. The spectrum of the Moon impactor matches the Chinese booster better than the SpaceX booster. Given the dynamical evidence cited by Bill Gray, we feel that our spectral observations are consistent with a Chinese origin.”

“Radar will help pinpoint the impact location better as the booster is getting tossed around by solar radiation pressure,” Reddy told Inside Outer Space. “It will still hit the far side of the Moon around the Hertzsprung crater area, but the impact point might shift a kilometer or so either way.”