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21-12-2019 - Happy Holidays and a Happy New Year!

To celebrate the end of this year, please find below a message from our Principal Investigator, Didier Barret, and our Project Manager, Vincent Albouys:


Dear colleagues and friends,

Here is the time again to wrap up another year of the life of our beautiful X-IFU project. 2019 was clearly very important for X-IFU, after the successful Instrument Preliminary Requirement Review in April and the successful Athena Mission Formulation Review earlier in November. Athena is now on a safe path towards mission adoption. It was only one year ago that the X-IFU consortium was formally appointed by ESA, and its organization also successfully passed through those two reviews.

As we are cruising into phase B, priorities are also set for ramping up the technology demonstration activities (e.g. the Detector Cooling System), consolidating the interfaces of the X-IFU with the science instrument module, freezing the instrument performance requirements. All of this is required for the writing of the red book in support of the mission adoption, scheduled for November 2021, prior to which the Instrument System Requirement Review is expected to take place at the beginning of 2021.

And of course, in 2020, we shall all embark on a mission to reduce the carbon footprint of X-IFU related activities by at least a factor of 2, with a goal of reducing it by 4.

So, may 2020 be as successful as was 2019.

On behalf of the X-IFU Consortium, we wish you happy holidays and a happy New Year!

Best regards,
Didier and Vincent


17-10-2019 - The X-IFU Gazette #12 has been released!

The 12th issue of the X-IFU Gazette has been released!

For this issue, our contributors from IRAP, CNES and the University of Geneva have prepared some great articles about the latest updates on the instrument, its sub-systems and the consortium.

You will find below the table of content:

  1. Editorial
  2. A successful CM10 in Toulouse
  3. What is PaCSXI2?
  4. Interfaces: The core of system engineering
  5. Microvibration – Macroscopic approach
  6. CM11: April 6th to 10th in Liège
  7. Key measures to reduce our travel footprint
  8. The Swiss contribution to Athena X-IFU
  9. Bio: Stéphane Paltani

23-09-2019 - The X-IFU Consortium meeting #10

The 10th X-IFU Consortium Meeting was hosted by IRAP in Toulouse from Monday 16th to Friday 20th of September. Participants met during various splinters and all together for the two days of plenary sessions. The programme was rich in topics related to activities triggered by the Instrument Preliminary Requirement Review (IPRR), which was held and concluded positively before the summer. Overall, it was agreed that the level of definition of all corners of the instrument keeps raising. Additionally, this was the first consortium meeting led by the recently appointed Project Manager from CNES, Vincent Albouys.

An important upcoming activity for the project is the Mission formulation Review (MFR) which will be carried out over the next months by the European Space Agency. The instrument itself will not be under review as the objective of the MFR is mainly to confirm the feasibility of Athena. It will be concluded by a board meeting scheduled for November 12th.

Of great significance, the X-IFU Consortium board agreed to reduce the number of physical meetings and optimize each of them in order to lower by at least a half the travel footprint of the project. From now on, we will move to only one consortium meeting a year, together with two meetings of the X-IFU project managers. This proposal was introduced by the Principal Investigator, Didier Barret, who provided members of the Consortium with a tool to estimate their own travel footprint and raise their awareness on their own environmental impact.

On a lighter note, the whole consortium got to enjoy the X-IFU Cuvée “A la Thien” which was selected by our very own X-IFU wine selection committee to celebrate the successful IPRR of the project.

Thanks to the hard work put in by the entire consortium, the X-IFU is on the path to its next milestone, the Mission Adoption Review, which will be preceded by the System Requirement Review. The next X-IFU Consortium meeting will be held in April 2020, jointly hosted by the Centre Spatial de Liège and the University of Liège in Belgium.

X-IFU Consortium Meeting #10

28-05-2019 - The X-IFU Gazette #11 is online!

The 11th issue of the X-IFU Gazette has been released!

This issue of the X-IFU newsletter will come back to the Instrument Preliminary Requirement Review (IPRR), which the X-IFU successfully completed on April 11th, with the joint ESA-CNES review board meeting held at ESTEC. This success has been a major achievement by the team, but now, time has come to take on the actions identified by the review panel. Thien Lam-Trong will come back with his take on the actions to be carried out. At the end of the day, this is the tax-payer money which enables us to fund the ambitious project that X-IFU is. This is why we need to explain to our citizens what the X-IFU is, which unique science it will address, what it is all about. A short movie introducing the X-IFU has just been released on the social network world wide, together with a press release announcing the success of the IPRR. Morgane Hébert will present the overall approach followed in the X-IFU movie. To close up the IPRR process, the 9th Consortium meeting was held in Grenoble between April 15th and 18th: I will summarize the main outcome of the meeting in my article later. As of May 13th, Vincent Albouys was appointed as the new X-IFU Project Manager. I wish a warm welcome to Vincent, who will introduce himself in this issue. We are now actively preparing the X-IFU 2019 Cuvée. I will provide you with some information in this newsletter. Finally, the X-IFU relies on a strong contribution from our NASA colleagues. Rich Kelley will present the overall US contribution to X-IFU, and introduce himself at the end of the newsletter.

Didier Barret
X-IFU Principal investigator


12-04-2019 - Instrument Preliminary Requirement Review : SUCCESSFUL!

The Instrument Preliminary Requirement Review of the X-IFU has been declared successful by the joint ESA and CNES review Board, yesterday on April the 11th.
Over 4 months, through different steps, the X-IFU has been evaluated by a panel formed by ESA and CNES senior experts. The consortium members have been compiling over 5000 pages of documentation in support of the review. They had to provide answers to the so-called review item discrepancies. The project team agreed on the actions to be pursued towards the next milestone of Athena, being the Mission Formulation Review. 

After 4 years of phase A,  the X-IFU team can be proud to move into the second phase of the project development ! The phase B, the preliminary design phase will start now, and is expected to end in late 2021, in time for the Athena Mission Adoption Review.

Congratulations to the whole X-IFU team for this outstanding achievement!

21-01-2019 - New appointments within the consortium

Jiri Svoboda from the Astronomical Institute (Czech Academy of Science) has been appointed board member, and Jan Soucek from the Institute of Atmospherics Physics (Czech Academy of Science) appointed Instrument Co-Investigator. This is the first step of the formal entry process of Czech Republic in the consortium.

On the Finnish side, following the completion of the ICC, Seppo Korpela from the University of Helsinky have been appointed Instrument Co-Investigator.

The formalisation of the Finnish and Czech contributions in Athena X-IFU marks a new step, an official recognition for the teams working on the project.

21-12-2018 - Merry christmas and happy new year!

2019 X-IFU

Time has come to close 2018. This has been another very important year for X-IFU with the formal appointment of the X-IFU Consortium by ESA. Most, if not all activities have focussed on the preparation of the upcoming IPRR, and many significant progresses have been achieved in all corners of the instrument (technology, design…). All this is now being documented in the IPPR data pack which already counts over 4000 pages, split in more than 100 documents, demonstrating the breadth and extent of the work done.

2019 promises to be important as well, with the IPRR followed soon after by the MFR. Let us hope that everything goes smoothly, but we have all reasons to be proud as we have an X-IFU entering the IPRR with performance comparable to or in some areas exceeding the ones that were promised to the community back at the time of the Athena mission proposal. Thanks so much to Thien and the whole CNES team for leading the project, and thanks to all the consortium partners for their dedication and unfailing support to the project. 

I do hope that you will have some rest during the Christmas break and let me wish you a merry Christmas and a very happy new year !
Thanks and all the best,

Didier Barret

Principal Investigator

PS: Thanks to Morgane for the X-IFU new year card with a simulated X-IFU cluster observation in the background (courtesy of E. Cucchetti et al.)

14-12-2018 - Athena X-IFU becomes an official consortium!

After more than four years of existence as a proto-consortium, on December 11th, 2018, following the successful completion of the instrument consortia confirmation process started in July, ESA formally appointed the X-IFU Consortium to provide the X-IFU for the Athena space X-ray Observatory: the second large mission of the ESA Cosmic Vision science program. This is a major achievement from the whole X-IFU team, made possible through a clear support from the 11 ESA member states involved in the instrument development. This is also a major step towards the adoption of the mission in late 2021.
The X-IFU consortium is now gearing all its efforts towards the preparation of the Instrument Preliminary Requirement Review to be held early next year. 

Didier Barret
X-IFU Principal Investigator

17-10-2018 - The X-IFU Gazette #9


September was a rather busy month for X-IFU. Following the X-IFU Consortium meeting #8 held in Geneva on the second week, the Athena bi-annual conference took place in Palermo on the fourth week. It was the opportunity to present the X-IFU progresses to the community and see in return how the community gets prepared to do science with X-IFU. Several talks highlighted the revolutionary potential of the X-IFU in many science corners of high-energy astrophysics. In the same month, we had to prepare the Instrument Consortia Consolidation (ICC) data pack, to be delivered to ESA on October 1st. The ICC is a rather light process led by ESA by which we expect the two instrument consortia to be formally recognized and appointed. This is an exercise focused mostly on programmatic issues, to ensure that the Athena Lead Funding Agencies (LFAs) are ready to support the overall Athena study phase and related activities (e.g. technology demonstration) until mission adoption. Following the data pack delivery, on October 5th, the ESA executives discussed the content of the ICC data pack with the Athena LFAs. As a very positive outcome, all X-IFU LFAs confirmed to ESA that they are ready to sign letter of endorsement for their proposed contribution. The whole process should be concluded by the next November ESA Science Program Committee. In parallel to the above activities, the CNES project team is consolidating the new Dewar baseline configuration to be submitted to the Instrument Preliminary Requirement Review (I-PRR) (see Alice contribution). On the programmatic front, ESA, JAXA, CNES and IRAP decided jointly to baseline JAXA as the provider of the 2K Joule-Thomson coolers. Finally the whole consortium is now focusing on writing documentation for the IPRR, which is expected to kick-off early February (see Thien contribution).

Didier Barret
X-IFU Principal Investigator

To address the practical preparation of the I-PRR in the frame of this gazette may be very boring for the writer and the readers. It would be more interesting to look back down the path that we have traveled to get here. The I-PRR is the milestone which allows us to present our way to manage the project, our set of requirements, the preliminary definition of the XIFU and the justification of our choices and the expected budgets (and their compliance to requirements). The signature of the X-IFU phase A is the intrinsically hard engineering to be performed because of the combination of an innovative instrument with a very high spectral (energy) resolution together with a cooling system needed to cool the detector to near absolute zero Kelvin. The difficulty is dramatically amplified by different factors: the X-IFU is not the whole spectrometer, the X-IFU doesn't have a physical unity and is composed of several physical parts. All these units shall be integrated together only at the level of the Payload Module (SIM, Science Instrument Module).

Both the heritage from other projects and the fragmentation of the development lead to implement a bottom-up approach at the beginning of the phase A. This approach has been a major handicap to reach the huge required level of performance and to implement the design-to-mass process imposed by the System constraints of Athena (the lift capability of the launcher).So, we have implemented an additional top-down process by realizing the flowdown of the requirements keeping in mind a balanced sharing of the pain. Optimization is the keyword in the system engineering of the X-IFU. The word optimization should be understood as a global optimization at the X-IFU level and higher levels. It shouldn't be understood as a combination of locally optimized units. Thanks to the collective effort within the whole Consortium, we did overcome all the difficulties and we can now move with confidence towards the X-IFU-PRR.
Thien Lam Trong
X-IFU Project Manager

CM8 Group Picture

The eighth X-IFU Consortium meeting was hosted by the University of Geneva. It span from September 10th to 14th. As usual, the meeting consisted of splinter meetings and plenary sessions. Beside the XSAT splinter and some technical meetings on JAXA coolers and on the Detector Cooling System, one splinter meeting was devoted to the preparation of the Instrument Preliminary Requirement Review (IPRR) documentation. The X-IFU Consortium Board met twice to prepare the Instrument Consortia Consolidation documentation, and iterated on the critical technologies and designs to be demonstrated before adoption.

The plenary sessions lasted two full days, giving sufficient time to review the status of the Athena mission, the baseline configuration of the instrument, and the status of all X-IFU subsystems. The last morning session of the meeting focused on science and performance related topics, and was concluded by presentations on the way forward to the IPRR. Let me take this opportunity to thank again the University of Geneva, and more particularly Enrico Bozzo, for hosting so smoothly the whole meeting in the beautiful city of Geneva. The next Consortium meeting will be in Grenoble, hosted by CEA-SBT.
Didier Barret
X-IFU Principal Investigator

SRON organized the Critical Design Review of the FPA-DM on September 17th-18th 2018. These two days were the opportunity to discuss the evolution of the design. FPA DM design is amply extensively described in the documents provided to the review group and most significant points were presented during the review. Let us remind here that the FPA-DM is a very early model of the FPA which has not the ambition to be fully representative of the flight model, especially the very end performance. However, thanks to the FPA-DM, it will be possible to demonstrate many other parameters, especially the behavior of the FPA when submitted to stringent environment. This will contribute to lower the technical risks on subsequent EM and FM models.

Françoise Douchin
Instrument engineering manager
Hervé Geoffray
Detection chain expert

The Dewar of X-IFU is a closed cryostat whose main function is to thermally insulate and actively cool the FPA and the detectors at the required temperatures, from the SIM ambient temperature. This implies to provide mechanical support not only to the FPA, but also to the cryogenic chain units requiring proximity to the cold parts (sub-K cooler, mechanical coolers cold heads and some of their compressors). Another function is to provide protection to sensitive cold parts from the outer environment.
From the EMC point of view, the Dewar participates to the shielding of the FPA signals and the low temperature measurement signals. This implies to gather in a single Faraday cage the Dewar outer vessel and the electronics hosting the reading of these signals (WFEEs, RTUs), and requires that these boxes be mechanically supported in the same assembly as the Dewar, with EMC continuity. The limitation of FPA harness length for electrical reasons (1.5 m) also acts for a Dewar carrying the WFEEs. In total, the Dewar has to carry roughly 120 kg of cryogenic chain units and 50 kg of detection chain and sensitive signals reading boxes.
Furthermore, the Dewar protects detectors and thermal filters from contamination, and the latter from acoustic loads, on ground and during launch, and so includes a vacuum-tight vessel compatible with launch loads.

Combining the functions of vacuum-tightness and mechanical support on the structure of the outer vessel has reached a technical limit with last summer evolution of the Dewar thermal architecture. With the addition of a passive shield cooled at 200 K via SIM radiators (IPCS), and the resulting increase of Dewar mass and volume, the mechanical design became marginal with respect to modal and strength criteria, within the allocated mass.

One introduced a concept of a new truss-kind structure, external to the closed vessel and dedicated to mechanical support, in order to alleviate the outer vessel. Several options are possible, according to units deported from the vessel to the truss: either only warm boxes, or also PT compressors (beneficial for microvibration limitation), or also PT compressors plus coolers cold heads (this last one complicating the definition of the coolers flange interface with outer vessel).
A trade-off between the three combinations of truss structure and lightened tight vessel, all satisfying stiffness and strength constraints, is conducted with respect to a mass criterion, and shall soon bring out the Dewar structure baseline for I-PRR.
Alice Pradines
Dewar manager


As their main contribution, JAXA's will provide two types of Joule-Thomson (JT) coolers, 2K JT and 4K JT, and their drive electronics. JT coolers utilize JT process which is an expansion of gas with enthalpy conserved.  Ideal gas will not change its temperature with this process, but real gas will.  At room temperature, Helium gas gets warmer by the process but when it gets colder than its “inverse temperature” (about 55 K for Helium at a 0-pressure limit), the temperature is decreasing.  Therefore, JT coolers requires pre-cooling by other cooling mechanism. Concerning the X-IFU pulse-tube coolers provided by ESA, they will pre-cool the Helium gas to about 15K. The vapor pressure will decrease very rapidly below 4 K and 2 K for 4He and 3He respectively, which determines the lowest temperature achieved by JT coolers. JT coolers consists of JT orifice which separates Helium of different pressures and through which Helium flows and expands, compressors which create pressure difference and Helium flow, and heat exchangers where the circulating Helium gas is effectively pre-cooled.

JAXA started development of space mechanical coolers in 1980’s with cooperation with Sumitomo Heavy Industries.  So far two 4K JT coolers have flown in orbit: in the SMILES mission on ISS, and in the SXS mission on Hitomi (ASTRO-H). A 2K JT cooler was originally developed for the infrared mission, SPICA and will also be used for the CMB mission, LiteBIRD.  The one for X-IFU requires longer lifetime than all of those missions. We consider that the present JT coolers can satisfy the 4.25 lifetime requirement of Athena, however it has not been proved by tests. Thus JAXA is conducting further lifetime tests and developments.
The Japanese X-IFU members consists of a team of scientists and an engineer from JAXA and two Japanese universities. With the expertise of the Hitomi SXS, they will also contribute to the cooling system design, calibration of the instrument, and science. Backup cryogenic readout SQUIDs are also being developed in collaboration with SRON and VTT
Kazuhisa Mitsuda
X-IFU Co-investigator

meDr. Kazuhisa Mitsuda is an X-IFU consortium board member and he is leading the Japan’s contribution. He is a professor at Institute of Space and Astronautical Science of JAXA located in Sagamihara, and a professor at Graduate School of Science, University of Tokyo. He is appointed Program Director of Space Science at ISAS. He was the JAXA PI of the SXS onboard Hitomi. The recent main objectives of his research group in astrophysics are the soft X-ray diffuse background and the hot interstellar medium. They extended their analyses of Suzaku data to constrain keV-range emission from dark matter in the halo of our Galaxy. They also develop TES X-ray microcalorimeters and the readout electronics.  They deployed an energy-dispersive X-ray spectrometer using a TES array for a scanning transmission electron microscope at National Institute of Material Science in Tsukuba for X-ray micro analysis.