In the field of X-ray astronomy, the XRISM (X-ray Imaging and Spectroscopy Mission) marks a new era. This space telescope, launched on September 6, 2023, is the result of a collaboration between NASA, the Japan Aerospace Exploration Agency (JAXA) and the European Space Agency (ESA). XRISM is equipped with Resolve, an instrument designed to deliver X-ray spectra with unprecedented precision. Unfortunately, a hatch that doesn’t open prevents it from working.
A past of challenges and hopes
Suzaku was launched by the Japan Aerospace Exploration Agency (JAXA) in July 2005. This X-ray telescope was designed to study energetic phenomena in the Universe, such as black holes, supernovas and galaxy clusters. Suzaku had unfortunately encountered technical issues shortly after its launch. Its spectrometer had in fact stopped working due to a failure of the cooling system, which had considerably limited its initial capabilities.
Despite this loss, Suzaku was able to continue his mission thanks to his other functional instruments, thus contributing to a better understanding of the extreme phenomena of the universe.
Hitomi, launched in February 2016, represented another leap forward in X-ray telescope technology. Featuring a high-resolution X-ray spectrometer and other advanced instruments, Hitomi promised to provide unprecedented details of the processes energy of the Universe. The mission aimed in particular to study galactic winds, galaxy clusters and high-energy X-ray sources with unparalleled precision.
However, shortly after its launch, Hitomi also suffered a series of catastrophic failures. In March 2016, a series of errors in the attitude control system notably caused a rapid and uncontrolled rotation of the satellite. Attempts to stabilize Hitomi had failed and the spacecraft ultimately disintegrated in orbit.
Suzaku and Hitomi’s experiences, however, were crucial to the development of XRISM. The lessons learned from the failures and successes of these missions have indeed made it possible to improve the design and reliability of the instruments of this telescope dedicated to X-rays. Unfortunately, here again, it seems that everything is not going as planned.
A trapdoor problem encountered by the XRISM telescope
Resolve is the core instrument of XRISM, launching in 2023. It is a high-precision soft X-ray spectrometer, designed to measure the properties of X-rays emitted by celestial objects with unprecedented energy resolution.
To operate, Resolve uses advanced spectrometry technology called microcalorimetry. Unlike traditional X-ray detectors that convert X-ray photons into electrical charges, this instrument measures X-rays by converting their energy into heat. This heat is then detected and measured with extreme precision, which makes it possible to determine the exact energy of the observed X-ray photons.
The main current concern in this mission is Resolve’s opening hatch. This hatch, initially designed to protect the spectrometer during the terrestrial phases of the mission, was in fact not not open as expected once the telescope is in orbit. The other instruments work as expected, which still allows JAXA and NASA to collect valuable data.
A real risk
The two space agencies now plan to continue operating XRISM as is for eighteen months with the aim of collecting as much data as possible, before attempting to open it again. However, such a maneuver carries several serious risks that could damage the telescope.
First, opening the hatch could require the application of a significant mechanical force. Such force could then damage the actuators or other mechanical components of the telescope. Actions required to dislodge the trapdoor, such as shaking the telescope, could also introduce vibrations or shaking that would affect other sensitive components.
Another risk is that of temperature change. To try to dislodge the trapdoor, it may indeed be necessary to warm up the telescope. However, the Resolve cryostat must be maintained at extremely low temperatures to ensure the spectrometer functions properly. Heating could thus compromise this condition and potentially damage the instrument.
Finally, if the hatch is opened in an uncontrolled manner, this could lead to a rapid depressurizationwhich would disrupt the operation of the cryostat and affect the entire cooling system.
Ultimately, space agencies JAXA and NASA will need to carefully weigh the risks and benefits before attempting to open Resolve’s hatch again.
