Add FITS keywords

[kelle]

It would be helpful to add the FITS keywords in Table 1. (Similar to Table 1 of the SpectrumDM document.) I'm updating this table as I work on this issue.

Field	Primary FITS Header Keyword
RA	RA_OBJ
Dec	DEC_OBJ
target_name	OBJECT
t_min	TSTART
t_max	TSTOP
t_exp_min	??
t_exp_max	??
t_exp_total	EXPOSURE?
delta_t_min	TIMEDEL?
delta_t_max	TIMEDEL?
t_resolution	TIME_RES

Field	Science Extension FITS Header Keyword
n_observations	NAXIS1 (assuming time is first axis)
type_of_data	TTYPE2 (assuming flux, RV, etc is the 2nd axis)

[kelle]

also relevant, STScI's light curve metadata page, which has made some other choices: https://outerspace.stsci.edu/display/MASTDOCS/Light-curve+Metadata. cc @ttdu

[kelle]

Also useful, this imageDM file.
imagedm-obscore.pdf