ACC summary Temperature dependency of ACC data TUD

ACC summary Temperature dependency of ACC data • TUD provides all available GPS-derived linear accelerations to VZLU • End of January – end of May • To be used for validation of temperature correction by VZLU à Target date: 24/06/2014 • VZLU produces temperature corrected linear acceleration data • Some problematic periods with large number of steps and spikes may be omitted • Data sets will be made available to TUD and Ales Bezdek for validation à Target date: 02/07/2014 à Does the temperature correction work well for all periods and all S/C? If not, under which conditions does it work well? à Do the parameters of the temperature correction model optimized for one period produce good results for other periods? Further decisions to be decided in teleconference ~ 04/07/2014. Note: ESA & DTU as Prime (Poul Erik) in cc

ACC summary Temperature dependency of ACC data (continued) • TUM provides STR-derived angular accelerations to VZLU à End of January – end of May, all S/C à Target date: 04/07/2014 • VZLU cross-checks model for temperature correction using STR-derived angular accelerations (note: priority remains on linear accelerations) à Target date: 01/08/2014 • Continue to improve temperature correction • Treatment of steps, etc. in L 2 depends on temperature correction in L 1 b

ACC summary Steps, etc. • Cause for sudden changes in bias (and scale factors) remains unclear • Flag detected steps, spikes, pulses, etc. at L 1 b, but do not correct (should give indication when characterization of instrument changes) • Treatment at L 2 is open issue • Continue to investigate steps (we do not give up!) Request for macro model Messages for scientific users • New temperature correction gives promising first results, in particular for alongtrack axis (ongoing investigations) • Swarm C provide significantly better acc data than Swarm A and B • Accelerometer data contains unexpected large number of steps and other disturbances that are not understood (physical cause not clear, treatment of steps under investigation) • Accelerometer data not yet ready for general user community (release date unclear)

ACC summary Recommendation for access to à house-keeping data (BUS and AOCS) à FOS daily reports (for step investigations) à Indicate location of accelerometer temperature sensors in L 1 b documentation à Temp. corr. Test data will be made accessible to Cal/Val teams à Processing including temperature correction needs to be documented (algorithm, input parameters, etc. ) à Investigate smoothing of accelerometer data at L 2 (~10 s) à Action: Distribute latest version of L 1 b product definition Issues with data sets observed: à Data sets contain zeros at beginning and end (S/C mass, frontal area) à S/C mass show mass variations (positive and negative!), should be fixed