The description of the concept how to plan SCIAMACHY operations in SODAP adresses

1.) planning concept
2.) measurement planning
3.) SCIAMACHY external requirements
4.) Instrument configurations

In the first part of the Commissioning Phase, the Switch-On and Data Acquisition Phase (SODAP), SCIAMACHY executes the functional and performance checkout and performs initial calibration & monitoring measurements. The interleaving of these types of activities is caused by the requirements to investigate the detector signals under different hardware and thermal configurations. The selected approach allows to generate a database of calibration & monitoring results from the very beginning of the mission onwards. For SCIAMACHY SODAP ends with the implementation of the final flight states at about L+120 days. This is much longer than SODAP for most of the other instruments onboard ENVISAT. However, all these instrument have their calibration measurements planned after the SODAP part of the Commissioning Phase.

The overall planning concept is sketched below.

SODAP operations planning concept

• ENVISAT System SODAP Plan

This is the driving planning document for SODAP. It assigns activity windows with a granularity of orbits to instruments and spacecraft. Within these windows an instrument may either be operated mission planning driven or procedure driven. For SCIAMACHY mission planning driven operations invoke the MEASUREMENT TIMELINE mode, i.e. the generation of measurement data. Procedure driven activities are those where pre-defined Flight Operation Procedures are executed by operators at the FOCC to achieve a particular instrument task.

In SODAP rules do exist which reduce the degrees of freedom for assigning instrument activities to orbit windows. These include e.g.

• not more than 2 instruments requiring operator assistence can be operated in parallel (non-assisted operations, i.e. MPS driven, may be executed orbits without assistence)


• critical activities must fall under Kiruna visibility


• operations requiring long coverage are assigned to combined Kiruna/Villafranca orbits

The ENVISAT System SODAP plan is maintained by ENVISAT.

• SCIAMACHY On-board Operations Plan - SCOOP

The SCOOP provides SCIAMACHY's planning down to the level of procedures. It is primarily engineering oriented. The details of the engineering activity in the SCOOP allow the operators at the FOCC to prepare the sequence of procedures. For time intervals where SCIAMACHY runs in MEASUREMENT mode the SCOOP does not list individual timelines but leave this to the SCOMP (see below).

The SCOOP is controlled by Astrium-SCIA in close cooperation with ENVISAT SODAP and SOST. Particularly the orbits whit merged procedure and MPS driven activities require careful harmonization.

• Engineering Background Activities

A number of monitoring engineering activities is not SODAP specific but must be executed for the whole mission, starting close after switch-on of the instrument. These are

• APSM health check


• RRU monitoring


• OA temperature monitoring


• PMD/SF ADC calibration

The background tasks are not explicitly mentioned in the SCOOP but invoked by procedures on defined timescales. Upon analysis of the monitoring results, it may be required to interrupt the nominal SODAP plan and implement corrective activities (e.g. decontamination). All engineering background activities are developed under the responsibility of Astrium-SCIA.

• SCIAMACHY On-board Measurement Plan - SCOMP

The SCOOP equivalent plan for SCIAMACHY's MPS driven operations in SODAP is the SCOMP. It lists on orbit level the individual timelines to be executed in order to achieve certain commissioning objectives. Additionally, the configurations, which run sequentially during SODAP, can be derived from the SCOMP. No engineering activities are included. SCOMP and SCOOP together provide a complete view of what is planned for SCIAMACHY in SODAP.

In case of re-planning, the SCOMP must be re-adjusted. This may require close cooperation both with the SCOOP and the ENVISAT System SODAP plan. As with the SCOOP, the SCOMP is maintained by Astrium-SCIA.

Information related to planned events in the SCOOP/SCOMP and the history of the actually executed operations can be found on the dedicated web page provided and maintained by Astrium-SCIA.

Of prime interest for the science and engineering groups involved in the analysis of measurement data from SCIAMACHY SODAP is the concept of Measurement Planning. This is a subset of the aforementioned planning concept. The concept follows a top-down approach consisting of 3 major steps. These are

• definition of SCIAMACHY measurement objectives for SODAP (all SCIAMACHY partners)


• definition and implementation of these objectives via SODAP specific states and timelines (Astrium-SCIA)
• implementation of the specific states and timelines in the mission planning environment and generation of the files to be provided to the operational ENVISAT ground segment (SOST)

The entity listed in brackets are responsible for the particular step.

Top-down approach for SCIAMACHY SODAP measurement planning

The figure above displays a large number of SCIAMACHY external planning requirements (blue shaded boxes). These have to be considered in all three steps of the planning activities.

• SODAP objectives

The various groups involved in the Commissioning Phase (SODAP) defined the measurement goals = objectives for the first months of in-orbit operations. From the large number of proposed objectives two reviews selected those with the highest priority. The accepted objectives formed the basis for the next planning step, i.e. the definition and implementation of SODAP specific states and timelines. As the objectives required the instrument to be in certain hardware configurations, the sequence of cover openings and SRC door release was the result of trade-off considerations on objective level.

• SODAP specific states and timelines

The external requirements to be fulfilled are

• boundary conditions by ENVISAT System SODAP plan (e.g. high data rate availability for particular measurements)


• harmonization of MPS driven operations with procedure driven operations as defined in the SCOOP


• Kiruna visbility to ensure dump of measurement data with subsequent NRT delivery
  
• monthly lunar visibility to plan moon related objectives


• solar azimuth for the settings of scan parameters in ASM diffuser states

The SCOMP reflects the actual status of these requirements. However, the planning front-end at SOST has to deal with additional requirements, which can only be implemented in the SCOMP in an iterative process between Astrium-SCIA and SOST.

• Operational planning files

In the preparation of the operational planning input to ENVISAT during SODAP, SOST has to consider

• reference orbit definition as outlined in the ROE file


• constraints for subsolar measurements as listed in the SSCO file


• orbital lunar visibility for the generation of moon related timelines (e.g. to define correct timeline duration)


• capacity of Data Distribution System (= satellite data link) to ensure availability of measurement in NRT


• orbits with NRT requirements to be synchronized with actual Kiruna visibility

In SODAP these requirements shall be known about 1-2 weeks prior to operations, at the latest.

During SODAP, SCIAMACHY's status is characterized by CTI Configurations. Each of these define a specific

• hardware status: covers, SRC door


• thermal status: OBM, detectors


• measurement parameter tables: SODAP specific and pre-defined states


• timelines: SODAP specific and pre-defined timelines

With the start of mission planning driven operations, SCIAMACHY executes subsequent configurations. However the resulting configuration sequence is not consecutive as monitoring configurations are invoked several times after critical activities.

Whenever the configuration ID changes it is required to upload new sets of measurement parameter tables. As long as the configuration remains stable, the measurement parameter tables remain stable as well. Only in the case of the Basic Scan Profile table modifications occur within a configuration due to the limited number of basic scan profiles.

The configurations can be directly translated into SODAP Timeline Sets. All timeline sets have been defined such that there is minimum timeline exchange necessary during SODAP.