Space Sunday: telescopes, lunar plans and Voyager 2

An artist’s impression of the CHEOPS observatory. Credit: ESA

On January 29th, 2020, the latest mission to study planets beyond our own solar system opened its eye to take a first look, in what is the start of a 3.5-year-mission to examine stars with known exoplanets.

The CHaracterising ExOPlanets Satellite (CHEOPS) a joint European / Swiss mission, was launched on December 18th, 2019 by a Soyuz-Fregat from Guiana Space Centre in Kourou, French Guiana, together with a number of other payloads. It forms the first of ESA’s new S-Class (Small Class) missions, capped at a maximum budget of €50 million apiece. It’s a small mission not just in terms of cost, but also in its physical size: CHEOPS measures just 1.5 metres on a side. Following launch, it entered a 700 km Sun-synchronous polar orbit.

The completed CHEOPS prior to being shipped for launch. The telescope cover is the circular gold element. Credit: ESA

Once there, initial testing of the satellite commenced. These first confirmed that communications between it and mission control were all working correctly. Once these had been thoroughly tested, the command was sent to boot-up the primary computer system so it could be run through a series of diagnostics before the primary science components were initialised. These tests also included the vehicle’s temperature control systems and the primary elements of the main telescope system – a 30 cm  optical Ritchey–Chrétien telescope.

CHEOPS launched on December 18th atop a Soyuz Feegat rocket from Guiana Space Centre in Kourou

These initial commissioning tests culminated in the opening of the telescope’s primary baffle – otherwise known as its lens cap. This was the most critical aspect of the initial commissioning – if the the baffle failed to hinge open, the telescope would be unable to observe its target stars.

Fortunately, the opening went as planned, allowing the final set of tests to commence. Over the next couple of months, these will see CHEOPS take hundreds of images of stars – some with exoplanets, some without, in order to examine the measurement accuracy of the telescope systems under different conditions, and confirm its operating envelope. At the same time, this period of testing will also allow this mission team to further integrate all aspects of ground operations. Again, if all goes according to plan, some of this first light images will be released by the CHEOPS science team, and the end of the tests will see the telescope commence its primary operations.

While thousands of exoplanets have been discovered, few of them have been accurately characterised in terms of both mass and diameter. This limits our ability to fully assess their bulk density, which is needed to provide clues to there composition and their possible formation history.So to help us gain better data, CHEOPS will accurately measure the size of known transiting exoplanets orbiting bright and nearby stars. These are planets that cause dips in the brightness of their parent stars as they pass between the star and Earth.

By targeting known systems, we know exactly where to look in the sky and when in order to capture exoplanet transits very efficiently. This makes it possible for CHEOPS to return to each star on multiple occasions around the time of transit and record numerous transits, thus increasing the precision of our measurements and enabling us to perform a first-step characterisation of small planets.

– Willy Benz, CHEOPS principal investigator

The transit method offer a “direct” means of detecting exoplanets, but it is not the only option open to us. A second method, generally referred to as the radial velocity method, or Doppler spectroscopy, can detect planets “indirectly”, by directing the doppler shifted “wobble” in a star’s motion. Around 30% of all exoplanets have been detected by this method, but it can be somewhat less informative than the transit method. This being the case, another aspect of the telescope’s mission will be looking at stars where orbiting planets have been detected via the radial velocity method in an attempt to detect the planets by the more direct transit method and again, by repeated observations, allow scientists to start to characterised them.

As a whole, CHEOPS will be particularly focused on exoplanets characterised as “super-Earths” – those thought to be between Earth and Neptune in size, many of which may well be solid in nature. While it will be able to characterise these exoplanets with a new level of precision, its work will pave the ways for follow-up observations in the future by telescopes like the James Webb Space Telescope (JWST – operating in the infra-red), and by large ground-based telescopes like the 40m Extremely Large Telescope currently under construction, allowing them to both refine the CHEOPS data and add to it.

House Bill Pushes Mars over the Moon

Under the direction of the Trump Administration, NASA has been pursuing the goal of returning humans to the Moon in 2024. In doing so, the agency turned its attention away from an (admittedly confused and fluffily-defined) overall goal of sending to humans to the Moon and then onwards to Mars in favour of the lunar exploration goal.

However, in January 2020, the House Science Committee introduced a NASA authorization bill, HR 5666, that seeks to switch the focus of NASA’s human spaceflight efforts back towards Mars. This bill both de-emphasises the 2024 deadline for a human return to the Moon by NASA, it also seeks to directly ties all of NASA’s human operations on the Moon directly to the goal of sending humans to Mars.

The Moon to Mars programme shall have the interim goal of sending a crewed mission to the Lunar surface by 2028 and a goal of sending a crewed mission to orbit Mars by 2033.

– From HR 5666

Under current plans, the Lunar Outpost Platform, Gateway (LOP-G), occupying a halo orbit in cislunar space, is intended to be a staging area for missions to the lunar surface. This includes being used to assemble the lunar lander vehicles that would be delivered to it in sections via commercial launch vehicles. However, HR 5666 directs NASA to take “full ownership” of all lunar landings, using a fully integrated landing system to be launched directly from Earth to the Moon using the SLS Bock 1B launcher and the enhanced Exploration Upper Stage. The latter is unlikely to be ready for flight by 2024, thus contributing to HR 5666 de-emphasising that year as a target for their first crewed return to the Moon.

Under HR 5666, the Lunar Outpost Platform-Gateway (LOP-G) would become a staging post for Mars missions, rather than supporting lunar missions Credit; NASA

The 2024 time frame is also de-emphasised because HR 5666 requires NASA completes at least one uncrewed and one crewed test flight of the lunar lander – something NASA has thus far not built into planning. Because of this, HR 5666 points to the first crewed return to the Moon to take place in 2028, although it doesn’t expressly rule out NASA making a return to the Moon before that year. However, it does require that once NASA has reached the Moon, operations there should be directly related to human operations on and around Mars – particularly in the realm of human / robotic missions, developing in-situ resource utilisation (ISRU) capabilities, and similar.

The idea of using the Moon to develop ISRU capabilities for use on Mars is at best questionable. If nothing else, Mars has a carbon dioxide rich atmosphere, which, when combined with a modest amount of hydrogen, is an ideal feedstock for producing water, oxygen and fuel (in the form of methane).

Using the Moon to develop ISRU capabilities for Mars misses the fact that the Martian atmosphere can, with the help of a little hydrogen brought from Earth – be readily leveraged into water, oxygen and even fuel (methane). Credit: The Mars Society / NASA

In the meantime, since its introduction, the bill has been passed by the House Subcommittee on Space and Aeronautics – with minor amendments – and but put before the full committee for broader debate, where it has drawn strong criticism from NASA – particularly with regards to de-emphasising the use of commercial launchers and services, with the fully integrated lunar lander viewed as being an “ineffective” approach.

Whether or not HR 5666 will pass to the full House for final approval remains to be seen. However, it cannot be denied that pushing and pulling at plans to send humans back to the Moon or on to Mars like this doesn’t actually help with trying to maintain a focus on a given goal.

JWST to Face Further Launch Delay?

The James Webb Space Telescope (JWST) is one of the most exciting missions NASA has been developing to increase our understanding of the cosmos around us. It is also one of the most overwhelmingly complex.

Designed to operate in the a halo orbit around the Earth-Moon L2 position, JWST also involves the European Space Agency and the Canadian Space Agency. Once operational, it will be able to carry out a wide range of studies in the infra-red – including the ability to better characterise the nature of exoplanets and their atmospheres. However, such is the complexity of the telescope, it is now running far behind schedule, which I’ve unfortunately often noted in this column.

JWST deployment. Credit: NASA

Originally conceived in the 1990s and a “low-cost” replacement for the Hubble Space Telescope priced at an initial US $500 million, JWST when through a convoluted gestation period (including becoming the JWST), its costs gradually climbing through the years reaching a point where today, they’ve reached US $9.7 billion.

Much of the telescopes development has been fraught with issues which have frequently pushed the planned launch date back, as well as pumping up the programme costs. One of the most significant of these issues lay with the telescope’s communications systems  – vital to transmitting its findings back to Earth. These massively ate into the contingency periods built into the project time frame, forcing the launch date to be repeatedly pushed back. But despite these delays and set-backs, by August 2019, the two major elements of the vehicle – the telescope itself and its support bus (which includes a complex sun shield needed to protect the telescope and its instruments) – had been fully tested individually and integrated ready for final testing.

JWST during a recent deployment test of the layer sun shield system (seen protectively wrapped under the telescope’s folded primary mirror. Credit: NASA

In the most recent revision, made in May 2019, JWST’s launch date was revised to March 2021 – but now that date looks set to be revised further. In carrying out a further review of the project in January 2020, the Government Accountability Office (GAO) stated that due to the issues arising from the telescope’s systems integration, the chances of NASA meeting a March 2021 launch date stand at just 12%, but the agency has a 70% chance of meeting the launch date were it to be pushed back to July 2021.

However, rather than immediately insisting the launch date is revised to July 2021, the GAO has given NASA until late spring 2020 to see if they can clear some of the remaining technical hurdles and show that March 2021 is still feasible. At that time, a further review will be used to determine whether or not the launch date should be revised further.

Voyager 2 Hits a Fault – and Recovers

NASA’s Voyager 2 spacecraft, now in its 42nd year of operations and more than a year travelling in interstellar space, unexpectedly entered a fault protection mode that curtailed science gathering operations on January 25th.

Voyager 1 and Voyager 2 – relative distances from the Earth. Credit: NASA / ESA

The fault mode was triggered when a pre-planned instrument calibration manoeuvre failed, leaving two relatively high-power systems operating at the same time, placing an extreme strain on the craft’s now very limited power generation capabilities. As a result, a fault mode kicked in to help conserve Voyager 2’s nuclear RTG, shutting down all of the science instruments.

As the craft is some 18.5 billion km from Earth, two-way communications take a staggering 34 hours, so it took three days for engineers to get Voyager 2 to restore itself to normal operations, although at the time of writing it had yet to resume transmitting data from its instruments.

Given the critical nature of the power system – later this year Voyager 2 will have to switch to a “power sharing” mode, as it will only be able to operate one science instrument at a time, and the RTG will be incapable of providing sufficient power for any of the instruments by around mid-2025 –  the hope is that in the next few days, science data will start to be received once more, rather than the mission being forced into a premature “retirement”.

NASA’s Day of Remembrance: January 30th, 2020

In memory of all those from the US astronaut corps and who flew on US space missions, who have lost their lives while furthering the cause of exploration and discovery, including the crews of Apollo 1 and space shuttles Challenger and Columbia. “We have whole planets to explore, we have new worlds to build, we have a solar system to roam in. And if only a fraction of the human race reaches towards space, the work they do there will totally change the lives of all the billions who remain on Earth.” – Francis Scobee, Commander, Space Shuttle Challenger mission STS-51L.