Space Sunday: Artemis and JWST updates, solar power from space

A view of Earth taken by a solar array mounted camera on the Orion spacecraft on November 24th, a day before the spacecraft entered a distant retrograde orbit around the moon. Credit: NASA

NASA’s Artemis 1 mission, launched on November 16th, 2022, has become the first vehicle capable of carrying humans that far, to return to the vicinity of the Moon since Apollo 17 in 1972.

The Orion capsule reached the Moon on Monday, November 20th, the fifth flight day of the mission overall. At 12:44 UTC, the vehicle, swinging around the far side of the Moon and so out of communications with Earth, closed to within 130 km of the lunar surface and a velocity of 862 km/h. It then fired the single motor mounted on the vehicle’s service module for 2.5 minutes, the first engine burn designed to push the vehicle into a distant retrograde orbit (DRO).

The DRO is a path that loops the vehicle away from the Moon in the opposite direction to the Moon’s own orbit around the Earth. Confirmation of the manoeuvre’s success came as the vehicle cleared the Moon and resumed communications with Earth – returning a colour image of our home in the process.

The DRO provides a highly stable orbit where little fuel is required to stay for an extended trip in deep space to put Orion’s systems to the test in an extreme environment far from Earth.

– NASA blog post

A portion of the far side of the moon as seen from the Orion spacecraft on November 21st, 2022 during the Artemis 1 mission. Credit: NASA

An hour later, as the vehicle proceeded away from the Moon, it passed over a historic landmark – Tranquillity Base, the landing zone for Apollo 11 in 1969 at a distance of 2,227 km.  It continued outwards from the Moon with all systems functioning as expected. However, on Wednesday, November 23rd, all contact with the vehicle was suddenly lost and remained so for 47 minutes prior to contact being re-established.

The cause of loss-of-contact lay with the reconfiguring of the communications link between the spacecraft and NASA’s Deep Space Network (DSN) – the orbiting and ground-based communications network used to maintain contact with all of NASA’s operational missions. The reconfiguration should have been routine, having been carried out several times during the mission as DSN carried out its multiple duties, and at the time of writing it was not clear what caused the glitch.

looking back at Earth from beyond the Moon, November 2st, 2022. Credit: NASA

At 21:52 GMT on Friday, November 25th, Orion made its second DRO engine burn, one that lasted 82 seconds, sufficient to push the vehicle into its outward loop away from the Moon travelling at 396 km/h. This outbound leg of the flight saw Artemis 1 breaking the record for the for the farthest distance from Earth travelled by a human-rated spacecraft, surpassing the 432,000 km distance set by Apollo 13 in April 1971; Artemis will reach a maximum distance from Earth of 435,000 km on Monday, November 28th, the point marking the start of its return to close proximity to the Moon, which it will reach on December 1st.

The mission has not all been smooth sailing, however. As noted in my previous Space Sunday update, the launch facilities at Kennedy Space Centre suffered damage during the Artemis 1 launch, although at the time of that article, NASA had not confirmed how much damage had occurred on the mobile launch platform.

Immediately following the launch, NASA asked the media not to image or record the launch platform and tower, citing security issues and ITAR (International Traffic in Arms Regulation), sparking speculation (particularly among SpaceX fans) that the Space Launch System rocket have caused considerable damage to its launch facilities and was therefore somehow a “failure”.

The elevator stations at the base of the mobile launch tower used in the launch of Artemis 1, showing the extent of the damage with the protective blast doors entirely blown-in. Credit: NASA

Since then, however, NASA has completed an initial damage assessment exercise and has been more forthcoming. Whilst a more in-depth assessment is required on the internals of the launch tower structure, the initial assessment suggests the launch platform overall faired a lot better than expected, given the huge strain it was under (SLS generates more thrust and heat than either the space shuttle vehicles or the Apollo Saturn V at launch).

Several umbilical connectors at the ends of the tower’s arms looked to have suffered some damage, whilst the blast doors designed to protect the tower’s two personnel elevators and their shafts were completely blown in and a couple of the automated camera on the platform were blasted into vapour by the engine exhausts. Overall, however, the preliminary assessment has left NASA confident that the platform and tower can be repaired and strengthened ready for the Artemis 2 flight, currently slated for May 2024.

Other issues for the mission lay not with Orion, SLS or the launch platform, but with the ride-along cubesats also launched with the mission and released by the Interim Cryogenic Propulsion Stage (ICPS) used to put the Orion capsule in orbit and then send it on its way to the Moon.

Whilst the release of the 10 cubesats proceeded smoothly after the IPCS and Orion had separated, at least three encountered subsequent problems as they approach the Moon. One of these was the LunaH-Map, designed to map the distribution and abundance of water ice on the moon’s surface, failed to fire its engine as planned but may be able to be salvaged.

Also going astray were both of the Japanese cubesats, with OMOTENASHI, intended to test using solid rocket motors to land on the Moon was unable to complete its planned de-orbit and landing due to communications issues. However, as it has solar power capabilities and is in lunar orbit, it is hoped a further landing attempt can be made in March 2023. EQUULEUS, meanwhile, initially operated as expected, image Earth plasmasphere and the surface of the Moon before it encountered glitches in communication.

China to Use Space Station in Space-Based Solar Power Test

China has indicated it intends to use the newly-completed Tiangong space station to test key technologies required for space-based solar power (SBSP), using satellites to collect solar energy and beam it to Earth-based stations for distribution to power grids.

Space Based Solar power generation

The station’s robotic arms will be used to test on-orbit assembly of modules for a space-based solar power test system, Yang Hong, chief designer of the Tiangong space station said in a presentation at the ongoing China Space Conference.

Once assembled the test system will then orbit independently and deploy its solar arrays and other systems. It is likely to test and verify capabilities such as power generation, conversion and transmission.  The tests are intended to “promote breakthroughs in individual technologies, accumulate on-orbit experimental data, and make contributions to the realization of carbon peak and carbon neutrality,” Yang stated.

In 2020 China announced targets of peak carbon emissions by 2030, and carbon neutrality in 2060. A viable SBPS network could go a long way to making this possible. However, such a project faces significant technical challenges: energy beaming attenuation through the atmosphere; cost of solar power satellite development and launch; the size and cost of the ground receiving stations (a 5 GW receiving station will cost an estimated US $5 billion). However, the satellites would be in the region of 99.5% efficient in terms of energy gathering (compared to an average of 29% here on Earth), and solar is the ultimate green energy source.

Nevertheless, the China Academy of Space Technology (CAST), the country’s main, state-owned spacecraft maker, has indicated it plans to conduct a “Space high voltage transfer and wireless power transmission experiment in low Earth orbit in 2028. This is to be followed by a second phase experiment conducted in geostationary orbit, requiring accurate energy transmission over a distance of 35,800 km to Earth. This will start in the early 2030s, and will be followed in two further phases in 2035 and 2050 to commence space-based power generation of 10 MW and 2 GW respectively.

In addition, China’s Xidian University has already completed a  75-metre tall structure it calls the world’s first full-link and full-system ground test system for SBSP, and the Chinese government is funding research into construction of kilometre-scale objects, a key requirement for developing large-scale orbital solar array assemblies for solar power collection and transmission arrays.

China is the latest country (or group of countries) to outline an interest in turning to solar power generation: the European Space Agency (ESA) is developing research into the feasibility of SBSP, and the UK government claims it is backing the Space Energy Initiative, which includes orbiting a 40 MW solar power satellite in orbit by 2027 and delivering solar-based power generation to the UK grid by 2040.  The latter sounds great – other than the UK government has stopped short of providing the £16 billion required for the 2027 test system.

JWST Back to Full Operations

On August 24th, 2022, the  James Webb Space Telescope (JWST) experienced suffered a major malfunction with its Mid-Infrared Instrument (MIRI), forcing the mission team to take the instrument off-line. While the observatory could continue making observations and taking images in other wavelengths, the issue did limit JWST’s capabilities.

The MIRI issue came shortly after Webb was struck by a large micrometeoroid, damaging one of its mirror segments, resulting in  MIRI’s own adjustment mechanism to work much harder when the instrument operated in its Medium-Resolution Spectroscopy (MRS) mode.

It  has taken a while, but mission engineers have overcome the issue, allowing JWST to return to a fully operational status across all instruments and operating in all modes. To test this, JWST was put through a series of image-gathering operations, including turning its eyes towards Saturn’s largest moon, Titan.

Saturn’s moon Titan, taken by the JWST on November 4th or 5th, 2022 using its MIRI camera. Credit: Michael Radke / NASA

The image was processed and uploaded to Twitter by Michael Radke, a Ph.D. student who studies planetary atmospheres at John Hopkins University (JHU). According to Radke, the image was acquired between November 4th and 5th, which he doubled in scale and added red, green, and blue to represent different wavelengths (R = 4.8 um, G = 2.1 um, B = 1.4 um). These values were based on data on Titan gathered by the NASA / ESA Cassini mission’s Visible and Infrared Mapping Spectrometer (VIMS).

The image colours appear to correspond to the absorption spectrum of carbon monoxide (green), methane (blue), and nitrogen (red), the gases that make up the majority of Titan’s atmosphere. The apparent illumination in the upper left in the image is thought to be the result on Saturn’s upper atmosphere reflecting the light of distant Sol. Overall, the  image provides a glimpse of the types of science operations Webb will conduct with Titan and other bodies in our Solar System.

Its powerful instruments and near- and mid-infrared imagining capabilities will allow astronomers to study the chemical composition of atmospheres in detail. Titan is of particular interest because it is the only moon in our atmosphere with a substantial atmosphere – where the air pressure is roughly 50% greater than Earth’s. Like Earth, TItan’s atmosphere is predominantly composed of nitrogen gas (94%), with hydrocarbons like methane making up the second largest fraction (5.65%).

Titan is the only other body in the Solar System with a precipitation and evaporation cycle. However, where Earth has a water cycle, Titan has a methane cycle: the methane forms clouds in the moon’s atmosphere before falling as rain to replenishes methane lakes. In addition, Titan’s atmosphere is rich in chemical processes as hydrocarbons are broken down by solar radiation into their constituents (i.e., carbon, hydrogen, oxygen, and nitrogen) and then form new molecules that percolate and settle on the surface.

Titan’s atmosphere and surface also possess something that no body other than Earth does: a rich prebiotic environment and organic chemistry. For this reason, astrobiologists have suspected that Titan may be one of the most promising places to search for extra-terrestrial life. For these reasons, Webb needs its instruments in working order, particularly MIRI and the Near-Infrared Spectrograph (NIRSpec). These will obtain high-precision spectra from Titan’s atmosphere to observe these molecules and processes at work.

An artist’s impression of NASA’s Dragonfly rotorcraft in flight on Titan. Credit: NASA / APL

These studies will build on previous efforts by the joint NASA-ESA Cassini-Huygens mission, which studied Saturn and its satellites from 2004 to 2017. Both the orbiter and lander studied Titan’s atmosphere in depth and made many profound discoveries. The more detailed information that Webb will obtain will be used to study Titan’s seasonal cycles, leading to more detailed climatic models. This will help pave the way for missions like NASA’s Dragonfly rotorcraft that will launch for Titan in 2027, arriving sometime in the 2030s.

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