Prime Keys are:
	T_START is slotted 'ts_slot' using T_START_index
	LMIN
	LMAX
	NDT
DB Index Keys are:
	T_START_index
	LMIN
	LMAX
	NDT
All Keywords for series hmi.V_sht_modes_archive:
	T_START   	(time)	beginning of time period
	T_START_step	(float)	T_START step, =1d
	T_START_unit	(string)	T_START step unit
	T_START_epoch	(time)	beginning of slot 0 (MDI epoch)
	T_START_round	(float)	= T_STEP
	LMIN      	(int)	minimum spherical harmonic degree
	LMAX      	(int)	maximum spherical harmonic degree
	NDT       	(int)	number of points in timeseries
	T_STOP    	(time)	beginning of following time period
	T_OBS     	(time)	midpoint of timeseries, =(T_START+T_STOP)/2
	DATE      	(time)	time the record was last updated, ISO format
	QUALITY   	(int)	bitfield specifying various aspects of data quality, see ???
	MAPMMAX   	(int)	maximum m for remapping dopplergrams
	SINBDIVS  	(int)	number of increments in sin latitude for remapping dopplergrams
	MFLIPPED  	(int)	sign convention for m: 0 for MDI, 1 for GONG
	T_STEP    	(float)	time step
	VERSION   	(string)	version of data, used for retrieving obsolete versions
	CALVER64  	(longlong)	calibration version
Segments for series hmi.V_sht_modes_archive:
	archive   	   none	generic	tar file containing the full results from all iterations
Links for series hmi.V_sht_modes_archive:
	HISTORY   	STATIC	hmi.globalhs_history	processing history