# Time Series Table Format

Description of FITS tables intended for store of time series (light curves) or another time series data.

The table is created as output of `munipack timeseries` command.

The specification slightly follows SimpleTimeseries format (IMPORTANT: This link is intentionally dead due authors themselves. There is no widely accepted definition of a format for light curves and related affairs yet.) Generally, Munipack's format is a bit more simplified and restrictive.

# File Structure

FITS file structure
HDU | EXTNAME | Description
--- | --- | ---
0 |  | Dummy[†]
1 | TIMESERIES | Time Series Table
2 | CATALOGUE | Objects identification (coordinates)

[†] The first dummy extension contains keywords of identification HDUNAME, which is set mandatory to 'TIMESERIES', CREATURE is set to 'Munipack X.Y.Z' version and a link to this page as a comment.

# Time Series Table

The main table which stores the time series.

Time Series Keywords
Keyword | Value | Default | Description
--- | --- | --- | ---
EXTNAME | TIMESERIES | TIMESERIES | extension identifier
TIMETYPE | JD | JD | Type of TIME: JD (Julian Day), MJD (modified JD), HJD (heliocentric JD), phase φ[1]
TIMESYS | UTC | UTC | Time system
TIMEREF | GEOCENTRIC |  | Reference time point
TIMESTMP | MIDPOINT | MIDPOINT | time stamp = MIDPOINT,BEGIN,END[2]

[1] Definition of Julian (also other derived) days provides Julian day wiki page. The phase φ = {(t - t0)/P} is defined as fractional part ({x} = x - ⌊x⌋) of time difference HJD since the epoch t0 per period P.

[2] The time is labeled by timestamps (the elapsed time is T): at the begin t0 (BEGIN) up to finish t1 = t0 + T (END) time. The midpoint is computed as t0 + T/2.

Time Series Table
Column | Type | Description
--- | --- | ---
TIME | 1D | Time-like quantity[a]
EXPTIME | 1D | Integration time like quantity[b]
Qi | 1D | Quantity for i-th object[c]
QEi | 1D | Standard deviation of Q-i[c]

[a] Units of the time-like quantity in days (for H,M,JD). The phase has no units.

[b] The exposure time is directly copied from frames and units are (perhaps) seconds.

[c] Table can contain many physical quantities. For their meaning, see Photometry data table. The table can contains multiple columns of the quantities for all required objects.

# Object Catalogue Table

This extension contains equatorial coordinates of objects of TIMESERIES extension.

Object Catalogue Keywords
Keyword | Value | Default | Description
--- | --- | --- | ---
EXTNAME | CATALOGUE | CATALOGUE | extension identifier
REFRAME |  | ICRS | Reference celestial coordinate system
EPOCH |  | 2000 | Reference epoch for proper motion

Object catalogue Table
Column | Type | Description | Units
--- | --- | --- | ---
RAJ2000 | 1D | Right Ascension[§] | degrees
DEJ2000 | 1D | Declination[§] | degrees

[§] Coordinates are referenced for epoch of the observation. Fast-moving objects can evince visible coordinate differences.

## See Also

Time Series