After having reached final flight configuration, a strict configuration control mechanism is required to maintain the operational measurement status. Such a mechanism has been introduced with the start of the routine operations phase in the form of Operation Change Requests (OCR).

All three levels of measurement operations, i.e. mission scenarios, states and timelines are covered by the OCR mechanism. It allows to track modifications to the actual final flight configuration from the originator of the change request to the moment, when the modification becomes valid in-flight. Each SCIAMACHY program participant (user, agency, mission) may issue an OCR. The flow of the OCR is predefined and comprises:

• Thorough description of the requested change up to a level of detail which allows to derive implementation options. The OCR originator has to send the OCR to SCIAMACHY project management (DLR). All OCRs raised by the science community shall be endorsed by SSAG. This avoids the parallel processing of conflicting science related OCRs.
• SCIAMACHY project management forwards OCR to SOST with request for analysis. SOST analyses OCR. In case external support (e.g. industry, ESA) is needed, project management is informed accordingly. SOST proposes implementation options based on provided input. Additionally, affected sub-systems (e.g. data processing, interfaces) are outlined and implementation dates are provided.
• Project management receives SOST OCR analysis. In case external support is required, it is initiated by project management. The OCR analysis is finally sent back to OCR originator and SSAG for approval of the implementation option. The approval ensures that the originator's ideas are properly addressed and that no other science requirements (calibration, validation, data processing) are violated.
• Upon approval of SSAG and the OCR originator, SCIAMACHY project management, or associated review board, finally decides about OCR.
• SOST-DLR implements approved OCR in a timeframe as outlined in the analysis. After successful implementation, the OCR will be closed.

OCRs are required for all operations modifications which cause a deviation from the final flight concept. This is true for both permanent changes and test cases. The complete processing of an OCR as described above can be time-consuming, particularly when modifications are required on the level of on-board state and timeline tables. Therefore, OCRs shall always be raised well ahead in time.

A Word template of the OCR can be found here: OCR_template.doc.

Please note that changes of engineering related issues (e.g. requests for decontamination, thermal settings) do not require OCRs. They are dealt with via a separate interface between SCIAMACHY and ENVISAT/FOCC.