Japan will launch the XRISM telescope and SLIM Moon Lander: how to observe them

JAXA, the Japanese space agency, is preparing to launch two very different space missions from a single rocket: a new X-ray telescope that will spy on some of the hottest spots in our universe, and a small experimental robotic lander on the moon.

The telescope is called the X-ray Imaging and Spectroscopy Mission, or XRISM for short (pronounced like the word “chrism”). The moon mission is called Smart Lander for Investigating Moon, or SLIM. Here’s what you need to know about the launch.

When is the launch and how can I watch it?

XRISM and SLIM are scheduled to launch on an H-IIA rocket from Japan’s Tanegashima Space Center on Sunday at 8:26 p.m. EST (it will be Monday at 9:26 a.m. in Japan). JAXA is offering a live stream in Japanese and English on the agency’s YouTube channel starting at 7:55 p.m. EST.

SLIM’s trip to the Moon makes timing tight: there are only a few minutes each day when Earth’s orientation is ideal for the spacecraft to follow a trajectory that will put it into lunar orbit. Therefore, JAXA has a reserved launch period until September 15, in case liftoff delays cause the mission to miss its launch window.

What is XRISM?

This is a bus-sized telescope. JAXA is collaborating with NASA on this mission, with additional participation from the European Space Agency. XRISM will study cosmic X-rays which, unlike other wavelengths of light, can only be detected above the Earth’s atmosphere, which protects us from harmful radiation.

XRISM will use state-of-the-art spectroscopy to measure changes in the brightness of celestial objects at different wavelengths. This data will reveal information about the movement and chemistry of some of the most extreme cosmic places, like matter swirling around black holes, blistering plasma permeating galaxy clusters, and the remnants of massive exploding stars.

A key tool on board XRISM is Resolve, an instrument that will collect spectroscopic data with much higher resolution than X-ray observatories orbiting Earth. Resolve needs to be cooled to just a fraction above absolute zero in order to measure tiny temperature changes as X-rays strike the surface of the instrument.

A second instrument named Xtend will work simultaneously to photograph the cosmos with a resolution comparable to what our eyes could perceive if we had X-ray vision. As Resolve zooms in, Xtend zooms out, giving scientists complementary to the same X-ray sources over a larger area.

SLIM is a compact robotic lunar lander without astronauts on board. It’s about the size of a small food truck and weighs over 1,500 pounds at launch.

The lander’s mission is not essentially scientific. Rather, it is to demonstrate an accurate navigational system, aiming to settle approximately the length of a football field from a targeted landing site. The development of better landing technology would allow future spacecraft to land closer to rugged terrain of scientific interest.

Where are XRISM and SLIM going?

The space telescope will be placed in an orbit approximately 350 miles above Earth. Once there, the researchers will spend the next few months powering up the instruments and testing their performance. Scientific operations will begin in January and the first results of this data are expected in about a year.

You will have to be patient with SLIM on its journey to the Shioli crater on the near side of the Moon. The spacecraft will make a long circuitous journey of at least four months that will require less propellant. SLIM will take several months to reach lunar orbit, then spend a month circling the moon before attempting to land on the surface.