GRAPEVINE, Texas — NASA has selected an X-ray astronomy spacecraft to study black holes and other astronomical phenomena as the next flight in a program of small astrophysics missions, the agency announced Jan. 3.
The Imaging X-ray Polarimetry Explorer (IXPE) spacecraft, scheduled for launch in late 2020, will be a small spacecraft with three telescopes designed to measure the polarization of X-rays. Measuring how the X-rays are polarized can provide insights into the high-temperature environments where they are created.
“We cannot directly image what’s going on near objects like black holes and neutron stars, but studying the polarization of X-rays emitted from their surrounding environments reveals the physics of these enigmatic objects,” Paul Hertz, director of NASA’s astrophysics division, said in a statement. “XPE will open a new window on the universe for astronomers to peer through.”
July 08, 2019
CONTRACT RELEASE C19-018
NASA Awards Launch Services Contract for Groundbreaking Astrophysics Mission
NASA has selected SpaceX of Hawthorne, California, to provide launch services for the agency’s Imaging X-Ray Polarimetry Explorer (IXPE) mission, which will allow astronomers to discover, for the first time, the hidden details of some of the most exotic astronomical objects in our universe.
The total cost for NASA to launch IXPE is approximately $50.3 million, which includes the launch service and other mission-related costs.
IXPE measures polarized X-rays from objects, such as black holes and neutron stars to better understand these types of cosmic phenomena and extreme environments.
The IXPE mission currently is targeted to launch in April 2021 on a Falcon 9 rocket from Launch Complex 39A in Florida. IXPE will fly three space telescopes with sensitive detectors capable of measuring the polarization of cosmic X-rays, allowing scientists to answer fundamental questions about these turbulent environments where gravitational, electric and magnetic fields are at their limits.
NASA’s Launch Services Program at Kennedy Space Center in Florida will manage the SpaceX launch service. The IXPE project office is located at NASA’s Marshall Space Flight Center in Huntsville, Alabama and is managed by the Explorers Program Office at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, for NASA’s Science Mission Directorate in Washington.
For more information about NASA programs and missions, visit: http://www.nasa.gov
NASA LAUNCH SERVICES II - SPACE EXPLORATION TECHNOLOGIES. MOD 137: REVISES THE IMAGING X-RAY POLARIMETRY EXPLORER (IXPE) LAUNCH DATE FROM MAY 31, 2021 TO SEPTEMBER 15, 2021 AND TO PROVIDE INCREMENTAL FUNDING.This delay was not unexpected
The program has been sitting on this announcement for some time.
That launch date is less than a year from today.
The odds of it holding are not good. IMOWhat is the major factor of the delay? The spacecraft not being ready? SpaceX issues? Covid?spaceflightnow, July 2, 2020, by Stephen Clark:
"Coronavirus work stoppage likely to delay launch of NASA X-ray astronomy mission"As stated in the linked article it’s mostly the CoVid shutdown of MSFC impacting the assembly and delivery of the Multiple Mirror Modules. There was also some delay to the Italian detector modules due to travel restrictions, and probably work delays there, too.
The spacecraft build is fine. I am told that their jobs were a little easier during the MSFC shutdown because the daily status meetings were suspended.![]()
The article is a bit suspect. It has the old 540 km orbit altitude. It is posted above that the orbit has been raised to 600 km to increase the orbital lifetime. Lacking that makes me suspect how well sourced the article is.
There are other issues whose resolution may further impact the launch date.
NASA's Imaging X-ray Polarimetry Explorer Prepares for Environmental Testing
Despite COVID-19-related hurdles, NASA's newest X-ray astronomy mission is a step closer to launch. Engineers recently completed integration of the agency's Imaging X-Ray Polarimetry Explorer, or IXPE, at Ball Aerospace in Boulder, Colorado. Now, Ball will put the fully assembled observatory through a series of tests that simulate the harsh conditions the small spacecraft will encounter on its rocket trip into space in late 2021.
"Reaching this milestone is a testament to the experience, commitment, and expertise of the IXPE team and our partners around the world," said IXPE principal investigator Martin Weisskopf of NASA's Marshall Space Flight Center in Huntsville, Alabama, who first conceived of the mission 30 years ago. "We're all looking forward to providing world-class science and expanding our view of the X-ray universe."
IXPE is the first small satellite mission dedicated to measuring the polarization of X-rays from a variety of cosmic sources — from black holes to exploded stars and jets traveling near the speed of light. IXPE's polarization measurements will complement observations from other telescopes in space now, including NASA's Chandra X-ray Observatory, adding new details about the nature of these mysterious objects and the environments close to them.
Upon completion, the IXPE observatory will be shipped to NASA's Kennedy Space Center near Cape Canaveral, Florida, for launch from launch complex 39A on a SpaceX Falcon 9 vehicle.
Building IXPE during a Pandemic
A collaboration between NASA Marshall and the Italian Space Agency (ASI), IXPE consists of three identical X-ray telescopes, each containing a set of nested cylinder-shaped mirrors — known as "grazing incidence" mirrors — paired with a corresponding polarization-sensitive detector. IXPE's polarization measurements are made possible by new detector technology contributed by ASI. Marshall's responsibility was to build and calibrate the mirror assemblies and deliver them to Ball for assembly, integration, and environmental testing.
"As an international project, the IXPE team faced a lot of unexpected challenges in the face of the COVID-19 pandemic," said Janice Houston, lead systems engineer at Marshall. "To get here has really taken a lot of teamwork and working through challenges. We have learned a lot about overcoming logistical difficulties — how to ship the hardware from one place to another during lockdown and how to remotely supervise and monitor handling and testing."
In order to keep team members safe and healthy, NASA delayed assembly and calibration of IXPE's mirror modules in mid-March, 2020. The IXPE team developed a new schedule to allow the team to reorder its assembly and testing timeline and get the spacecraft ready for launch.
The mirror assemblies left Marshall the afternoon of Sept. 9, arriving at Ball on Sept. 10 to be integrated into the spacecraft. Under normal circumstances, Marshall's mirror module assembly team would help unpack and inspect the mirror modules after shipment. Instead, the team provided Ball with written procedures and video demonstrating post-shipment inspection, resulting in a successful integration.
With integration complete, IXPE will undergo environmental testing at Ball. Though each component of the observatory has been rigorously tested during development, demonstrating that the assembled flight hardware is able to safely pass through a simulated launch environment will be another significant achievement for the mission. NASA has worked carefully with its international partners to match the testing environment precisely to what IXPE will experience both on launch day, and when operating in orbit.
More about IXPE
NASA selected IXPE as a Small Explorer mission in 2017. IXPE is a collaboration between NASA and the Italian Space Agency, led by principal investigator Martin Weisskopf at NASA's Marshall Space Flight Center in Huntsville, Alabama. Ball Aerospace, headquartered in Broomfield, Colorado, manages spacecraft operations with support from the University of Colorado at Boulder. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the Explorers Program for the agency's Science Mission Directorate in Washington.

I just finished watching NASA's coverage of the IXPE launch (which was independent of the SpaceX coverage), and was disappointed that they never explained how an X-ray mirror works. It isn't a big shiny surface that most of us think of when we hear "mirror", rather a dense pack of concentric metal rings that barely refract the incoming X-ray photons. This also explains that long distance required from the mirror to the focal plane. They did a fine job explaining polarization, but nada on the mirror.
https://en.wikipedia.org/wiki/X-ray_telescope#Focusing_mirrors
Also, the coverage should have placed IXPE into the context of previous X-ray missions like Chandra and NuSTAR (and bonus points for proposed missions like Lynx).
I mean, they did have 75 minutes to fill.

It is nice to see that science observations have begun.
Note that this image is a composite of IXPE (purple) and Chandra (Blue) imaging data.
https://twitter.com/NASA/status/1493352575105703939
Less than a year after launching, NASA’s Imaging X-ray Polarimetry Explorer’s (IXPE) observations of a neutron star have led to confirmation of what scientists have only previously theorized: magnetars have ultra-strong magnetic fields and are highly polarized.
Scientists used IXPE to observe the magnetar 4U 0142+61, a neutron star located in the Cassiopeia constellation, about 13,000 light-years away from Earth. This is the first-ever observation X-ray polarization from a magnetar, a neutron star with the most powerful magnetic fields in the universe.
Astronomers found that the neutron star likely has a solid surface and no atmosphere. This is the first time that scientists have been able to reliably conclude that a neutron star has a bare solid crust, a finding enabled by IXPE’s X-ray polarization measurements.
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Scientists were surprised to learn energy levels can affect polarization.
“Based on current theories for the magnetars, we expected to detect polarization, but no one predicted polarization would depend on energy, as we are seeing in this magnetar,” said Martin Weisskopf, a NASA emeritus scientist who led the IXPE team from the mission’s inception until spring 2022.
Additionally, the polarization at low energies indicates that the magnetic field is so unimaginably powerful that it could have turned the atmosphere around the neutron star into a solid or a liquid.
“This is a phenomenon known as magnetic condensation,” said chairman of the IXPE’s magnetar topical working group, Roberto Turolla, with the University of Padova and University College London.
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For Weisskopf, it’s clear that IXPE’s observations have been critical.
“In my mind, there can be no question that IXPE has shown that X-ray polarimetry is important and relevant to furthering our understanding of how these fascinating X-ray systems work,” he said. “Future missions will have to be cognizant of this fact.”
Blazars are some of the brightest objects in the cosmos. They are composed of a supermassive black hole feeding off material swirling around it in a disk, which can create two powerful jets perpendicular to the disk on each side. A blazar appears especially bright from the perspective of our telescopes because one of its powerful jets of high-speed particles points straight at Earth. For decades, scientists have wondered: How do particles in these jets get accelerated to such high energies?
NASA’s Imaging X-Ray Polarimetry Explorer, or IXPE, has helped astronomers get closer to an answer. In a new study that was published on November 23 in the journal Nature, authored by a large international collaboration, astronomers find that the best explanation for the particle acceleration is a shock wave within the jet.
“This is a 40-year-old mystery that we’ve solved,” said Yannis Liodakis, lead author of the study and astronomer at FINCA, the Finnish Centre for Astronomy with ESO. “We finally had all of the pieces of the puzzle, and the picture they made was clear.”
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The new study used IXPE to point at Markarian 501, a blazar located aproximately 450 million light years away from Earth in the constellation Hercules. This active black hole system sits at the center of a large elliptical galaxy.
IXPE watched Markarian 501 for three days in early March of 2022, and then again two weeks later. During these observations, astronomers used other telescopes in space and on the ground to gather information about the blazar in a wide range of wavelengths of light including radio, optical, and X-ray. While other studies have looked at the polarization of lower-energy light from blazars in the past, this was the first time scientists could get this perspective on a blazar’s X-rays, which are emitted closer to the source of particle acceleration.
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Scientists found that X-ray light is more polarized than optical, which is more polarized than radio. But the direction of the polarized light was the same for all the wavelengths of light observed and was also aligned with the jet’s direction.
After comparing their information with theoretical models, the team of astronomers realized that the data most closely matched a scenario in which a shock wave accelerates the jet particles. A shock wave is generated when something moves faster than the speed of sound of the surrounding material, such as when a supersonic jet flies by in our Earth’s atmosphere.