Psyche to Psyche: Journey to a Metal World

Six years into the future and 177 years after its discovery, the massive asteroid 16 Psyche will receive its first visitor from Earth. The aptly named Psyche mission will enter orbit of its target world and perform intensive studies for 21 months across four different orbits. The data the Psyche orbiter collects will yield new insights into the early history of planetary formation, and most importantly will provide us our first big glimpse into a new medium of geology. 16 Psyche is not a world of rock or ice, it is not a world of rubble like asteroids Ryugu and Bennu – 16 Psyche is a world enriched in metal. The asteroid’s unusual composition led to an understanding that this world may be the exposed core, as of writing this is no longer the case. As for the mission itself, Psyche was to launch last year, on a very efficient trajectory it would arrive at Psyche after just four years later in 2026, this is also no longer the case. Much has changed since Psyche’s approval, and refamiliarizing oneself with the state of the mission and a modern understanding of its target is important.

On the 5th of October, 2023, Psyche will become the 14th and latest mission launched as part of NASA’s Discovery Program. Discovery is NASA’s program for lower cost planetary science missions, wherein teams of scientists and engineers can submit proposals for potential future missions. Discovery Program selections occur around once every four years, and begin with an Announcement of Opportunity which outlines the general time frames proposals must be launch-ready in. From there, usually around a year later, a handful of finalists are selected from the submissions and receive a multi-million dollar grant to be further developed by their teams. In 2015, Psyche was among the finalists for Discovery 13 and 14. Alongside it were DAVINCI and VERITAS, Venus atmospheric and orbiting probe proposals, NEOCam, an asteroid detecting space telescope, and Lucy, a tour of Jupiter’s trojan populations. Each concept received $3 million to continue their studies. 2017 marked the announcements for the missions that would officially become Discovery 13 and 14, and those missions were Psyche alongside its contemporary mission, Lucy. Lucy launched successfully back in 2021, despite some issues with solar array deployment, the craft is healthy and will conduct its first planetary science operation later this year with a flyby of the small asteroid, Dinkinesh.

Contrastingly, Psyche missed its planned launch window in 2022, software issues arose with the space probe’s guidance, navigation, and control system, prompting a stand down from launch in June of 2022. By missing its launch window and with the cost to correct the fault unknown, Psyche entered a period of uncertainty regarding whether it would even get a chance to launch at all. Continuing the mission would result in significant cost overruns, and a need to be replanned for a later launch window and arrival date. The spacecraft would have to be reworked to survive a longer cruise and operational phase, which also means more time on NASA’s Deep Space Network, a longer time spent paying JPL to get the spacecraft flight worthy, and an increase to risk. There were also some concerns raised that the GN&C system fault found on Psyche could be shared with other spacecraft, and potentially result in widespread delays both government and commercial, however this does not seem to be the case. All of these aspects had to be considered before Psyche could get the go ahead to continue, the mission’s delay represented a major setback for a program meant to have a low cost and high speed. NASA organized a review board the same month the delay was announced to weigh the costs of continuing against the losses of terminations in order to determine if the Psyche teams could pull the mission back together for a 2023 launch. This continuation/termination review process lasted until October 28th, 2022, at which point NASA officially announced the mission will continue. This continuation was not without cost however, last year VERITAS, selected as Discovery 16 in 2021, had its launch delayed three years to 2031, and this year development of the mission was frozen, with teams receiving enough funding to remain employed, but not enough to progress the mission towards launch. The delayed launch also resulted in a review process for the smaller mission, Janus, which was to launch as a rideshare with Psyche. Janus would’ve seen two small cubesats dispatched to two different NEO asteroid systems to perform flybys, however the change in launch window meant this mission could no longer be carried out, and the mission was officially canceled on June 11 this year. Both spacecraft are now in storage and may be repurposed for a different mission in future.

After an additional year of setbacks, corrections, and further work to get the spacecraft into a launch-ready state, JPL is now on track for Psyche’s October 5th launch. On August 3rd the spacecraft’s massive twin solar arrays were permanently installed. In a multi week long process Psyche will be loaded with the xenon propellant that will enable its journey to the asteroid belt. Psyche uses electric propulsion in the form of four hall thrusters, further cementing electric propulsion as the standard for deep space missions. Getting the payload into space will be handled by SpaceX’s Falcon Heavy rocket, Psyche’s launch will mark the first planetary science mission handled by Falcon Heavy.

After its launch in October, Psyche’s first science phase will be primarily composed of testing of its experimental Deep Space Optical Communication (DSOC) system. DSOC aims to demonstrate the use of a beam of photons in communication back and forth with a spacecraft, and will be the first time such technology is tested in deep space, (beyond the Moon). By increasing the speed at which data can be transferred between a spacecraft and ground stations, the total amount of information which can be transported in a given amount of time can be multiplied dramatically, hopefully by anywhere from 10-100x. This prospective technology could change the way we communicate with deep space missions at no cost to mission mass or volume, a “game changer.” Demonstration of DSOC will begin about a year post-launch, and continue until Psyche’s encounter with Mars in 2026. This gravity assist will boost Psyche towards the asteroid belt, where it will rendezvous with Psyche, and potentially yield some exciting imagery along the way. The Mars gravity assist will mark the planned end of the DSOC demonstration. However, if DSOC proves itself its mission may be extended, perhaps becoming a part of nominal mission operations, as has happened with Ingenuity in relation to the Mars2020/Perseverance mission.

Operations at 16 Psyche will begin in 2029 with a 100 day approach phase. During this time Psyche will use its imaging systems to give us our first look at this world. This is when we will get our first good look at Psyche’s shape, its large-scale surface features, and a solid grasp on its rotation rate and axial tilt. Orbital insertion follows, and Psyche will find itself in the first of four alphabetical orbits around its namesake asteroid. In the original plan for its 21 month mission, Psyche was to be slowly lowered towards its target of study, starting with Orbit A, the highest, and ending with Orbit D, a low orbit of 16 Psyche. Orbit A is an orbit 700 km above 16 Psyche, and is focused on preliminary mapping of 16 Psyche, such as identifying major surface features. This high orbit phase of the mission would last for 56 days. Orbit B, 290 km above 16 Psyche, and Orbit C, 160 km above Psyche, were to follow after Orbit A and these orbital phases would’ve lasted for 80 and 100 days respectively. The final orbit, Orbit D, is just 85 kilometers above 16 Psyche, and in it Psyche would use its spectroscopy instruments to provide a detailed look into the asteroid’s surface composition, this is also the orbit least inclined to the asteroid’s equator. Orbit D was the final 100 days of Psyche’s planned mission, which had it launched in 2022. 

Due to Psyche’s year-long launch delay, this operational phase has had to be reworked somewhat. The purpose of the sequential lower orbits was for data collected in each orbit to inform how the craft is navigated to its next orbit and how it will keep itself stationed there stably. The issue lies in 16 Psyche’s axial tilt, as the asteroid rotates on its side, much like Uranus, meaning that in different phases of the year there are different regions of permanent day and night. Had it launched in 2022, the spacecraft would’ve arrived at 16 Psyche when its equator was roughly aligned with the Sun, near the local equinox, and every region would get roughly the same amount of time illuminated by the Sun. Because of the three year delay in its arrival, this will no longer be the case. Psyche mission planners have had to make compromises to minimize both the navigational risk to the spacecraft, and loss of scientific data due to delayed arrival. This new mission plan aims to maximize the yield from Psyche’s science instrumentation, balancing time between the orbiter’s spectrometers and imagers to do their work in the proper lighting conditions. The result is an extension of the mission at 16 Psyche to 26 months instead of 21, across the same orbits but in a different order. Now after spending time in Orbit A, and proceeding onto Orbit B, Psyche will now descend all the way down to Orbit D. After spending time in Orbit D, it will rise back up to Orbit C, and then return to Orbit B again. Both phases spent in Orbit B are now referred to as Orbit B1 and B2 in order of occurrence.

While the data is diminished somewhat from the previous plan, the Psyche mission will still yield an incredible bounty of data on the nature of 16 Psyche. The nature of 16 Psyche has been called into question in recent years. The article Observations, Meteorites, and Models: A Preflight Assessment of the Composition and Formation of (16) Psyche, published in February of 2020, casts considerable doubt on the notion that the asteroid is indeed a remnant core, calling to attention that for Psyche to be pure iron-nickel it would need to be highly porous, unlikely for an object its size. Instead of being pure metal, 16 Psyche is more likely to be a mix of metal and silicate material. 16 Psyche is highly reflective, indicating the upper layers of its surface do contain high amounts of metal. This reflectivity is higher in some regions than it is in others, and the precise reason for this is not known, but one popular suggestion is that these metallic regions are the result of ferrovolcanism, iron volcanoes. The paper Ferrovolcanism on Metal Worlds and the Origin of Pallaistes, published in September of 2019, suggests that Psyche may be a differentiated body, (meaning it is layered), where metallic materials were spewed onto an otherwise rocky surface by volcanic processes. If this process is confirmed by the mission, it would be an entirely unique geologic process to 16 Psyche, never before observed. It is not possible to say for certain what kind of world Psyche is or how it came to be until we get there, and no matter what is found the mission will surely yield new insights into the process of planetary formation. Luckily, the wait is not much longer before the journey begins.

It has been a long and complicated road to launch, and it has come with more than its fair share of setbacks, costs, and challenges. While the fate of VERITAS in response to Psyche’s increased costs is uncertain, as is the fate of the spacecraft that were to fly as Janus, and we cannot say if the Discovery Program may see further restructuring in the near future in response to Psyche’s issues, at the very least for Psyche itself the final steps are laid out, plain and clear. Space Scout looks forward to covering the launch in October, when NASA sends Psyche to Psyche, and begin the six year journey to a metal world.

Edited by Nik Alexander