University of Copenhagen

Niels Bohr Institute of Astronomy, Physics and Geophysics

Department of Geophysics

 

Juliane Maries Vej 30,

DK-2100 Copenhagen Ø,

Denmark. Date: 2001-10-01

Phone: +4535320582, Fax: +4535365357 Doc: goce_sl4_pm2.doc

 

DRAFT

 

ESA Project "Preparation of the GOCE Level 1 to Level 2 Data Processing"

 

Slice 4: Development and test of critical modules.

 

Report prepared for PM2.

 

Coordinator: C.C.Tscherning

 

Introduction:

 

Slice 4 deals with the Development and test of critical modules. These modules are needed for the development of the first prototype and the full prototype. These modules are initially identified in Slice 2 and more explicitly in Slice 3.

 

At the PM1 an action item was to define precisely a critical module. After consultation with the members of the team, it was agreed to define a critical module as a piece of software which is necessary for the development of the full prototype.

 

There are, however, many issues which are considered as critical, but not in terms of software: missing information, unsolved methodological problems, lack of full understanding of an issue and missing computational and staff resources. Such items are listed in the contributions to slice 2 and 3 but will not be dealt with here.

 

An important issue is also the methods/procedures for verifying the performance of the prototypes, including the availably of realistic test data.

 

 

Critical software modules:

 

From the input to Slice 2 available at present the following items have been found which may be described as critical modules according to the abovedefinition:

 

Task 1: Standards.

 

A satellite macro-model is required in order to accurately model the nongravitional forces during periods without linear acceleration measurements. However, this is a piece of missing information and not in itself a module missing for the development of the prototype.

 

Task 3: Aid to preprocessing.

 

For the computation of topographic effects a module is missing which may calculate these effects on all observables. A prototype (such as TC) may use spherical approximation, but the final version not.

 

Gross-error check.

 

Implemenation of procedures for simultaneous use of several datatypes in the gross-error check. Prototype (GEOGRIDX) is not able to do this.

 

Task 4: POD.

 

No specific critical software modules have been identified. However a modification of existing POD software in order to satisfy the very high demands of GOCE is needed.

  1. Conversion of drag to one unique reference.
  2. Apriori models of gravity, tides and atmosphere.
  3. Satellite model (see also Task 1).
  4. Incorporation of common-mode accelerations, DFC/attitude, macro model in reduced dynamic POD.
  5. Methodology, parameter set, ambiguities (Kinematic POD).

 

Task 5.1: Gravity field recovery using direct method.

 

Software to support Archiving facility and communication links (on ground).

 

Implementation of new SSG data processing modules, new interface with GINS/EPOS software. New strategy for adjustment method.

 

 

Task 5.2: Gravity field recovery, time-wise.

 

No critical software modules have been identified at this moment.

 

Task 5.3: Gravity models SW.

 

Module for the treatment of SST observations as potential differences or accelerations, including elimination of non-inertial forces.

 

For the integration(iteration method, a module for the estimation of the errors and error-covariances is missing.

 

Task 6. Solution Evaluation.

 

Method (and thereby software) to evaluate error-covariances lacking.

 

Task 9. Computation of regional solutions .

 

No critical software modules have been identified.