Dear IROWG colleagues,

At the latest Coordination Group for Meteorological Satellites (CGMS) plenary meeting (June 2026), IROWG was notified that CGMS Working Group III (WGIII) tasked IROWG with coordinating a scientific assessment of the impact of the decline in COSMIC-2 radio occultation (RO) observations expected as the constellation ages. The IROWG assessment is to inform the next WGIII Risk Assessment Workshop (24–26 February 2027). FYI, IROWG is under CGMS-WGII (Satellite data and products), while WGIII is the Working Group on Operational Continuity and Contingency Planning. 

The action reads:

Action #

Actionee

AGN item

Description

Action feedback/closing document

Deadline

Status

54.01p_wgiii

IROWG

WGIII

IROWG to assess the impact of the decline in COSMIC data availability, possibly distinguishing between the respective contributions of low- and medium-inclination orbit, and analysing the number of RO required to mitigate the risk

4 June 2026
- A follow-up call will be arranged to better understand how the action item supports agency priorities
- IROWG can help coordinate an assessment
- The timeline for completing the assessment depends on the detailed plan for conducting the assessment

End of 2026

(9th WGIII RAWS: 24-26 Feb 2027)

OPEN

WGIII has indicated that “we do not need IROWG to weigh in on the potential acquisitions strategies for data, but rather to provide information about what data is needed to maintain capabilities and/or mitigate loss of COSMIC-2.The purpose of the action is for IROWG to provide information to WGIII in advance of the next Risk Assessment to inform WGIII discussion/evaluation of risk posed by degradation/loss of COSMIC-2 and, if needed, discussion of potential contingencies to mitigate loss of COSMIC-2. The questions WGIII would like the IROWG to answer are:

  1. From a scientific perspective, what is the minimum number of equatorial (low inclination) RO needed to maintain current performance of operational NWP
  2. Define what they mean by low inclination (clarify the orbital characteristics for low inclination so we can be sure we are all talking about the same thing)
  3. Identify if there are options to use increases in the number of non-low inclination RO to mitigate the loss of COSMIC 2 and if so, to be specific about how many additional occultations (be specific about number and distribution needed). "
The IROWG Co-Chairs will meet with WGIII shortly after IROWG-11 (September 2026) to provide an update on the community's progress. Therefore, we would like to begin gathering relevant information before the workshop and continue the discussion during IROWG-11.

We would greatly appreciate hearing from anyone who has:

We recognize that IROWG is an international scientific working group, and contributions are entirely voluntary. Existing analyses, ongoing work, and expert perspectives are all valuable.

If there is sufficient interest, the IROWG Co-Chairs would also be happy to organize an informal community discussion before IROWG-11 to exchange ideas and help facilitate discussion during the workshop.

If you have relevant material or would like to contribute to this assessment, please contact the IROWG Co-Chairs at your convenience.

Thank you in advance for your help and for supporting this community effort.

Best regards,

Hui Shao and Uli Foelsche, IROWG Co-Chairs
Tony Mannucci, IROWG Rapporteur