C-LEO means Connectivity in Low Earth Orbit. Its Call 2 ARTES route and Call 3 national route require different proposal processes. Checked 8 September 2026: Call 3 Stage One has closed; invited Stage Two applicants have a published deadline of 11 November 2026 at midday GMT. Existing Call 2 applicants should follow their separate UKSA and ESA checkpoints. C-LEO Call 3: national applicant guide C-LEO Call 2: ARTES applicant guide
Which C-LEO process applies?
| Question | Call 2: ARTES | Call 3: national |
|---|---|---|
| Funding envelope | £30 million in the UKSA call | Up to £42 million |
| Published full-proposal checkpoints | Historical indicative UKSA checkpoint: 25 September 2026, midday (GMT) as written. Historical indicative ESA checkpoint: 5 October 2026. Existing applicants must confirm their actual UKSA/ESA stage and instructions | Stage Two: 11 November 2026, midday GMT, for invited applicants only |
| Starting maturity and intended progression | Starting TRL 4–5 emphasis, aiming at TRL 7 or above | Guide emphasis on proposals at TRL 4–6, with progression towards TRL 7 and above. The guide also considers higher-TRL proposals. See the guide/FAQ wording conflict below |
| Submission authority | UKSA national support process and ESA ARTES instructions | UKSA national application forms and associated annexes |
The table summarises the two applicant guides, not a complete eligibility assessment. Call 2 labels its schedule indicative and uses “midday (GMT)” in September; do not silently convert that to UK summer time. Confirm the exact instruction through the programme before submission. For Call 3, check UK establishment, lead status, relevant technology, match funding, project dates and required forms in the national guide. Do not reuse the funding-rate assumptions of another call.
The retained 22 October 2026 review of the Call 3 guide and FAQs found differing starting-maturity wording. The guide overview targets proposals at TRL 4–6 and says higher-TRL proposals will be considered. Section 7 excludes applications starting below TRL 4. FAQ 1.5 says “Projects must start at TRL 4-6 and reach TRL 7 or above”, while FAQ 2.25 says “Your project must have a starting TRL of 4” and describes progression above 7. These statements do not establish one universal exact starting threshold. Check guide §7 and FAQ 1.5 alongside FAQ 2.25, and obtain programme clarification for a real submission. Keep the starting evidence and proposed progression separate. The fictional antenna example awards no TRL.
How do we connect the proposal to assessment?
Call 3’s Stage Two criteria give 20% each to strategic fit, value for money, catalysing investment, and innovation and technical feasibility; project management and benefits have 10% each. Technical feasibility asks for differentiation, approach, readiness progression and deliverables. Project management asks for milestones, risk, schedule, leadership and governance. Guidance Note E
Create an internal claim record for every major promise. Link the technical gap to the task that addresses it, the cost basis, the proposed evidence and the milestone decision. Then reconcile those records with the official application sections. The workbook is a preparation aid: submit only the documents and annexes permitted by the programme.
What supports the antenna proposal?
Fictional preparation example; all values are proposed assumptions, not achieved results or UKSA requirements. A team proposes an antenna control assembly, revision B. Its bench prototype has exercised the command path, but thermal performance and representative host integration remain unverified. The intended output is a credible demonstration plan, not a self-awarded readiness level.
| Record | Proposed content | Gap / accountable role |
|---|---|---|
| ANT-01 requirement | Commanded beam state reached within 100 ms under the agreed interface and operating conditions | Systems lead must agree the timing boundary and conditions with the host. |
| Current evidence | In the scenario, a revision A bench trace covers the command path only | Verification lead must assess relevance to revision B; no environmental claim. |
| WP-2 planned work | Integrate revision B with a representative host simulator and execute the agreed timing test | Integration lead needs simulator access and the interface revision. |
| M-2 acceptance decision | Reviewed test report, configuration list, raw trace references and anomaly disposition | Technical authority decides whether the proposed criterion is met. |
| Industrialisation task | Review component availability and production test coverage for the intended design | Manufacturing lead owns the gap between demonstrator and repeatable product. |
If the host changes its command protocol after the bench run, keep the original trace but reassess its applicability. A completed task does not make its evidence valid for a changed configuration. Use the change-impact guide to connect the affected requirement, firmware, procedure and milestone.
Fictional ANT-01 claim row, retained internally
Claim: ANT-01 draft B, proposed 100 ms criterion with boundary still to agree
Planned assessed configuration: board B, FW-B v0.2, host simulator HOST-SIM-01 rev A
Planned procedure: TEST-ANT-01 v0.1, pending approval
Planned report: RPT-ANT-01 v0.1, reserved reference only, no run or result
Work: WP-2 integration, timing campaign, review and corrective work
Cost basis: task effort, simulator/fixture access and measurement support, quotations pending
Milestone: M-2 proposed evidence review, owned by the technical authority
Call 3 mapping: Stage Two Form technical/work-plan response
Budget mapping: Annex A: Budget Sheet, Proposed Milestone Table tab
Other official documents: Annex B: National Security, Annex C: Overheads Template and Annex D: Grant Applicant Checklist, as applicable under the guide
Bid owner checks the actual invitation and unchanged official templates. This row is not an extra annex.The official document names and milestone mapping above come from the Call 3 guide’s Stage Two and Budget Sheet sections, retained in the 22 October 2026 source review. Use the actual issued form and instructions for your application. The internal row does not establish eligible expenditure or an accepted milestone.
What should we reconcile before submission?
Compare the narrative, budget and schedule against the same work-package identifiers. Check that partner effort includes integration, review and corrective work, not just design hours. State which facilities and customer inputs are dependencies. Keep technical performance claims separate from commercial forecasts and show the basis of each forecast.
A systems lead should be able to follow one promise all the way to a planned result and owner. A bid lead should be able to explain why that work belongs in the relevant call and how it will be submitted. For supplier-specific scope, use the consortium handover checklist; for the distinction between current and target maturity, use the TRL evidence guide. Return to the UK funding route hub if the correct instrument is still unclear.
Connect the antenna proposal to its evidence
For the illustrative antenna package, connect revision B, the proposed thermal test and the host interface assumption to the technical claim they support. Review the missing evidence before adopting the proposal as a programme commitment. Arc’s connected programme model can organise that context; engineers retain the technical and approval decisions.
Frequently asked questions
Can I still submit a new C-LEO Call 3 Stage One bid?
The published Stage One deadline was 7 September 2026 at midday GMT. As checked on 8 September, that entry stage has closed. Stage Two is for invited applicants; possible supplier changes follow separate programme rules.
Are C-LEO Call 2 and Call 3 the same submission route?
No. Call 2 is an ARTES route involving UKSA support and ESA submission. Call 3 is a UK national grant call with its own forms, eligibility and timetable.
Does a successful test demonstrate the target TRL automatically?
No. Explain the technology, representative configuration, environment, critical functions and remaining limitations against the applicable readiness definition. A single result can leave major evidence gaps.
How should one technical claim connect to the proposal budget?
Give the claim, work package and milestone consistent identifiers across the narrative, costs and schedule. For the revision B antenna example, budget the host simulator, integration, agreed timing test, review and corrective work needed to support the promised result.
Can revision A bench evidence support the revision B antenna proposal?
It can describe the starting evidence, with its original command-path scope. Assess the hardware, firmware and host-interface differences before reuse; thermal or representative-integration performance remains a gap until applicable completed evidence supports it.
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