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Table 2.

Comparison of calibration methods and criteria.

Asikainen & Mursula (2011) and Asikainen et al. (2012) Sandanger et al. (2015)
α Factors provided for channelsa P1–P3 P1–P5
Separation in space between satellites <1° magnetic latitude and longitude at foflb and <10% relative difference in L-value Only compare satellites with <1 h separation in MLT
Separation in time between comparable satellites <30 s
Data used Instantaneous measurements (2 s resolution) Mean value of one month of data from whole orbit
Number of months data from new satellite is considered non-degraded 5 12
Method for obtaining time evolution Linear, 2nd order, 3rd order, PCHIPc fit with α vs. time, or as a function of ap index Iteration method using α vs. accumulated corrected integral flux

P6 is excluded in all studies due to relativistic electrons contaminating the measurements.


foot of field line (fofl) confining each satellite.


Piecewise Cubic Hermite Interpolation Polynomial (PCHIP), shape preserving interpolation.

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