TEMPO Warnings

PSRCHIVE makes use of tempo to generate polynomials that approximate the relationship between apparent topocentric pulse phase and time. The accuracy of this approximation depends upon the length of time spanned by each polynomial, TZNSPAN, and the number of coefficients, TZNCOEF.

If a PSRCHIVE program issues a warning like 

Tempo::Predict::generate WARNING rms=0.411525 microseconds
Tempo::Predict::generate http://psrchive.sourceforge.net/warnings/tempo
then is it is likely that either TZNSPAN should be decreased or TZNCOEF should be increased. These parameters can be set in the input ephemeris file; e.g. 
PSRJ           1909-3744
RAJ            19:09:47.4379988
DECJ           -37:44:14.31816
F0             339.31569275868954208
F1             -1.6147667945018354534e-15
DM             10.393214975272748697
[...]
TZRMJD         53477.971476731175557       
TZRFRQ         1400
TZNSPAN        120
TZNCOEF        15
Note that the span of the polyco is specified in minutes, and the minimum value of TZNSPAN accepted by tempo is 60. The updated ephemeris can be installed with 
pam -E updated.eph -e new filename.ar