Space Sunday: SLS, satellites and a rover

The Artemis 1 Orion MPCV and its European Space Agency service module sit atop the first NASA Space Launch System (SLS) on Pad 39B at Kennedy Space Centre, a full Moon framed between the vehicle and one of the pad’s lightning towers. Credit: NASA

NASA’s Space Launch System (SLS) has finally cleared the last significant hurdle in the preparations to launch the first of the vehicles on its much anticipated lunar flight.

On Friday, June 24th, agency officials declared the test campaign for the maiden vehicle to be almost complete after it finally cleared the critical wet dress rehearsal (WDR) test on a fourth attempt – the first three in May each ending with issues that forced NASA to roll the vehicle and its mobile launch platform back to the Vehicle Assembly Building (VAB) at Kennedy Space Centre, Florida, so both could receive modifications.

The final dress rehearsal started on June 20th, and concluded 20 seconds early due to a leak in a hydrogen bleed line. While this did not compromise the test itself, it did prevent 13 of the planned 128 command functions from being performed as a result. Most of these had been previously tested, so the curtailing any testing of them during the WDR was not seen as cause for concern.

However, mission managers opted to perform one additional test prior to rolling the vehicle back to the VAB for final inspections and launch preparations. This will be a test of hydraulic power units used to gimble the nozzles of the vehicle’s solid rocket boosters to provide directional guidance while the boosters are firing. One it has been completed, the roll-back to the VAB will be carried out on July 1st.

The Artemis 1 SLS vehicle sitting on its mobile launcher at Pad 39B, Kennedy Space Centre, imaged from orbit on June 18th, 2022 by a Maxar Earth observation satellite. Credit: Maxar Technologies

At the VAB, the vehicle and its launch platform will undergo a final post-WDR inspection, which will include replacing the seal responsible for the hydrogen leak. It’s expected that overall, the final check-out plus any required work will run through until early August. Providing nothing serious is found, the vehicle will be rolled back to the pad to commence 10-14 days final launch preparations. This will be in time to meet two immediate launch windows: August 23rd through September 6th (excluding the period August 31st-September 1st) and September 19th through October 4th, 2022.

The Artemis 1 mission is designed to fly an uncrewed Orion Multi-Purpose Crew Vehicle (MPCV) on 20+ day mission to cislunar space including 6 days in lunar orbit. It will be a preliminary check-out of Orion’s life support, propulsion, guidance and communications systems during an extended mission, prior to repeating the flight with a crew on board with Artemis 2.

CAPSTONE

On Monday, June 27th, NASA will be launching another mission to cislunar space.

The Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment (CAPSTONE), is a 25 kg cubesat the size of a microwave oven designed to study what is called a lunar near-rectilinear halo orbit (NRHO) – an extended elliptical orbit around the Moon that will bring the satellite to within 1,600 km of the lunar surface before lifting it away to up to 70,000 km. It is a similar orbit to the one that will be used by NASA’s planned Lunar Gateway station.

While extreme, such an orbit allows for continuous communications with Earth and allows for extensive study of the Moon. When placed in a similar orbit, Gateway will allow astronauts to reach almost any point on the lunar surface using suitable landing systems.

The CAPSTONE cubesat sitting on an engineering bench during testing of its solar arrays. Credit: NASA / Dominic Hart

CAPSTONE is due to be launched from New Zealand aboard a Rocket Labs Electron rocket at 10:00 UTC om Monday, June 27th, 2022. As the Electron is not capable of delivering CAPSTONE directly to the Moon, it will use the company’s Photon kick stage to push the cubesat into an extended 4-month flight to the Moon, where it will enter orbit on October 15th. The extended, slow flight will allow CAPSTONE to carry out a range of tests prior to reaching the Moon and is not reflective of the kind of transit time crewed flights will require to reach lunar NRHO (5-10 days).

Once in orbit around the Moon, CAPSTONE will spend a further 6-months studying the NRHO environment around the Moon and in communication tests both with Earth and with NASA’s Lunar Reconnaissance Orbiter, which has been orbiting the moon since 2009.

SpaceX Triple Header with a Touch of Mystery

SpaceX carried out three near “back-to-back” launches over the weekend of June 17th-19th, albeit from different launch complexes:

  • On Friday, June 17th, a Falcon 9 lifted-off from Pad 39A at Kennedy Space Centre, carrying aloft the company’s latest batch of Starlink satellites for deployment.
  • On Saturday, June 18th, a Falcon 9 lifted the SARah-1 radar imaging satellite to orbit on behalf of the German military, after lifting-off from Space Launch Complex 4E at Vandenberg Space Force Base in California.
  • On Sunday, 19th, the third launch lifted-off from Space Launch Complex 40 at Cape Canaveral Space Force Station in Florida, ostensibly to place the commercial Globalstar FM15 into a “parking” orbit as a back-up for the company.
A Falcon 9 lifts off June 17 carrying a batch of Starlink satellites, the first of three launches SpaceX performed over a little more than 36 hours. Credit: SpaceX

While all three saw the successful return and landing of the Falcon 9 first stage of each booster, the June 19th mission has raised eyebrows due to the apparent secrecy around it. The Globalstar FM15 is a relatively small satellite – just 700 kg – which should have allowed the Falcon first stage to return to the SpaceX landing zone at Canaveral; instead it landed on a drone ship at sea, suggesting it was flying a heavier payload that required greater thrust to push it to orbit.

SpaceX also did not cover the launch with anything like the kind of live streaming they generally put out for their launches; what footage that was put out suggested the vehicle was carrying an additional payload adaptor, hinting at a further payload – although nothing has been said to confirm or deny this.

Curiosity Returns Stunning Images, But Shows Signs of Age

NASA’s Mars Science Laboratory (MSL) rover Curiosity continues to explore “Mount Sharp”, the 5 km high mound of deposited material at the heart of Gale Crater as it approaches the 10th anniversary of its arrival on Mars.

While the rover – NASA’s first nuclear-powered vehicle to arrive on Mars – has been somewhat overshadowed by its sister rover, Perseverance, the discoveries it continues to make remain as fascinating as when it first set out to explore the floor of the crater in August 2012.

NASA’s Curiosity rover captured this view of layered, flaky rocks on June 2nd, 2022. It is believed they were formed by water repeatedly entering a small pond-like basin on the the transitional region of “Mount Sharp” currently being studied by the rover. Credit: NASA/JPL

For the pass year, Curiosity has been going through a transitional zone in which water-rich clay deposits give way to salty sulphates, suggestive of a zone where the waters that once occupied the crater did not reach the upper reaches of the mound, allowing sand dunes to form due the action of wind as the climatic conditions changed and the atmosphere became ever drier.

The transitional zone has been of significant interest to NASA and geologists due to the manner in which two different environments mix, with dry dune deposits combining with sediments deposited in layers over time by the action of water. These point to times when waters on these higher slopes of Aeolis Mons – as “Mount Sharp” is properly named – ebbed back and forth against the mound’s shoreline, forming pockets of water amidst the dryness, laying down the sediments in the process.

June 2022: a view back along the left side of the Curiosity rover captured by the imager on the the rover’s robot arm showing some of the damage to the left centre wheel. Credit: NASA/JPL

The challenge for geologists is trying to piece together the timeline against which the transition from wet to increasingly dry to dry occurred; if it can be determined, could help pin-down the period when free-flowing water on Mars began to be affected by the planet’s thinning atmosphere, and how atmospheric loss and water vapour loss interacted with one another.

Whilst approaching its tenth anniversary, Curiosity has suffered a few issues of late. On June 7th, the rover entered a “safe” mode after a temperature sensor started giving false readings, suggesting the rover’s electronics were overheating, causing it to shut down major operations. The issue was fixed by switching to back-up sensors, allowing the rover to resume normal operations.

Another view of Curiosity’s centre left wheel, seen from above, showing more the the damage wrought from 10 years of driving on Mars. Credit: NASA/JPL

Of a greater worry is the overall condition of the Curiosity’s six aluminium wheels. These have been suffering mounting damage as the rover’s mission has progressed, but at the start of June it was noted that the left middle wheel has suffered sufficient damage to start breaking its grousers (treads). While mission manager do not believe the grousers will disintegrate completely, tests have been underway using the ground test vehicle to see how the rover will operate should it have to operate on the rims of some wheels.

As it stands, the amount of damage on the one wheel is not reflected to the same degree on the other five. This has prompted the mission team to remain confident Curiosity can continue to function properly without any current need to alter its driving mode or to increase the number of wheel inspections being carried out (currently performed using the imager on the rover’s robot arm each time it racks up another 1,000 metres on its mission odometer).

Psyche On Hold

Psyche is both the name of a metal asteroid and of a NASA mission that was due to be launched this September / October to investigate it, but which has new been placed on hold.

Measuring some 226 km across, Psyche – or more correctly, 16 Psyche – sits within the asteroid belt between Mars and Jupiter. Unlike the majority of those asteroids, however, Psyche appears to be what might be part of a shattered planetesimal – a basic building block of a planet. This makes it an interesting study, as it could inform scientists about both the development of planets during the early history of the solar system, and the formative years of the solar system itself. First discovered in 1852, it was at the time only the 16th asteroid that had been detected.

An artist’s impression of the Psyche spacecraft. Credit: NASA

First identified as a deep space mission in 2015, the Psyche mission has been financed under NASA’s Discovery Programme and run by the Jet Propulsion Laboratory with Maxar Technologies responsive for building the vehicle. The size of a compact car, the spacecraft weighs 2.6 tonnes and is designed to use  solar electric propulsion in order to complete a 3.5 transfer flight from Earth to Pysche. Once there, it would enter orbit and perform 21 months of science observations of the asteroid – the first time a metal asteroid has ever been visited.

The mission has been put on hold as a result of the spacecraft’s navigation, guidance and control software falling behind in development, having only recently been completed and passed to the mission engineering team for loading onto the vehicle. However, there is no time to test it it post-implementation before the vehicle has to transferred to Kennedy Space Centres for integration with its Falcon Heavy launch vehicle.

Rather than rush ahead with the software untested on the actual flight hardware, NASA has decided to halt the mission. An independent review will now examine the software development programme to determine why it missed deadlines so badly, and to determine when next a launch attempt should be made: the next two occurring in 2023 and four in 2024.

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