1. Model evaluation with low-altitude GOCE densities
Sean Bruinsma
CNES - Space Geodesy
Toulouse, France
PREGO: ESA CONTRACT
/15/F/MOS
Adrian Jäggi, Daniel Arnold – AIUB, Bern, Switzerland
Noelia Sánchez-Ortiz – Deimos Space, Tres Cantos, Spain

2. Introduction
CIRA models are evaluated: NRLMSISE-00, JB2008 and DTM2013
GOCE density data from 11/2009 – 11/2013 is used ( km), scaled to HASDM (operational Air Force model)
Metric: mean, sigma, RMS and correlation of density ratio O/C
Evaluate long (years), medium (month) and short (day) time scales
Model: ‘C’
GOCE: ‘O’
Ratio O/C: ideally 1.00
GOCE (2009 – 2013):
Acc. resolution: 1·10-12 m/s2/Hz0.5
ion propulsion
GPS and SLR
inclination: 96.5°
Altitude: km
densities 0.1Hz, precision 1-2%

3. Introduction GOCE densities: Low altitude Low-medium solar activity
6-8am/pm local solar time
Models: solar proxies:
NRLMSISE-00: F10.7
JB2008: S, F10.7, M, Y
DTM2013: F30
ftp://ftp.cls.fr/users/previsol/solarflux/final

4. Long time scales – O/C
On time scales of year(s), JB2008 and DTM2013 are nearly unbiased
(mission design, lifetime estimation)

5. Daily time scales – O/C NRLMSISE-00
Mean / s of annual time series: / 0.051
of monthly time series: / 0.067
of daily time series: / 0.098

6. Daily time scales – O/C JB2008
Mean / s of annual time series: / 0.020
of monthly time series: / 0.042
of daily time series: / 0.066

7. Daily time scales – O/C DTM2013
Mean / s of annual time series: / 0.014
of monthly time series: / 0.037
of daily time series: / 0.061

8. Daily time scales – RMS of (O/C – 1)
Mean/s : / 0.027
Mean/s : / 0.038
Mean/s : / 0.047

9. Daily time scales – correlation DTM2013
No solar rotation period
Mean / s of daily time series: / 0.028
(NRLMSISE-00: / 0.033)
(JB2008: / 0.031)

10. Summary and Conclusions
High resolution GOCE densities available
CIRA models evaluated in the km altitude range
DTM2013 and JB2008 (NB: proxies!) most accurate and precise
NRLMSISE-00 biased (solar activity)
All models biased for lowest activity in , most NRLMSISE-00
Standard deviation of CIRA models at the 10% level (1-s)
High correlation, variation with solar rotation period reproduced
Representative results for all local times (using CHAMP, not shown)
Model errors at time scales of months: unexplained (ap/kp?)
Still large model error for enhanced-storm conditions