Units

Listed below are Units of Measurement, supported by TMT observatory framework and are available as Enumerated values. Units are optionally attached to Parameter Keys.

Type definition for Units can be found here

Default Units for Keys

The default unit for UTCTimeKey and TAITimeKey is second. For all the remaining keys, default unit is NoUnits.

SI Units

Name	Abbreviation	Description
angstrom	Angstrom	10 -1 nm
arcmin	arcmin	arc minute; angular measurement
arcsec	arcsec	arc second: angular measurement
day	d	day - 24 hours
degree	deg	degree: angular measurement 1/360 of full rotation
elvolt	eV	electron volt 1.6022x10-19 J
gram	g	gram 10-3 kg
hour	h	hour 3.6x10+3 s
hertz	Hz	frequency
joule	J	Joule: energy N m
kelvin	K	Kelvin: temperature with a null point at absolute zero
kilogram	kg	kilogram, base unit of mass in SI
kilometer	km	kilometers - 10+3 m
liter	l	liter, metric unit of volume 10+3 cm+3
meter	m	meter: base unit of length in SI
marcsec	mas	milli arc second: angular measurement 10-3 arcsec
millimeter	mm	millimeters - 10-3 m
millisecond	ms	milliseconds - 10-3 s
micron	µm	micron: alias for micrometer
micrometer	µm	micron: 10-6 m
minute	min	minute 6x10+1 s
newton	N	Newton: force
pascal	Pa	Pascal: pressure
radian	rad	radian: angular measurement of the ratio between the length of an arc and its radius
second	s	second: base unit of time in SI
sday	sday	sidereal day is the time of one rotation of the Earth: 8.6164x10+4 s
steradian	sr	steradian: unit of solid angle in SI - rad+2
microarcsec	µas	micro arcsec: angular measurement
volt	V	Volt: electric potential or electromotive force
watt	W	Watt: power
week	wk	week - 7 d
year	yr	year - 3.6525x10+2 d

CGS Units

Name	Abbreviation	Description
coulomb	C	coulomb: electric charge
centimeter	cm	centimeter
erg	erg	erg: CGS unit of energy

Astrophysical Units

Name	Abbreviation	Description
au	AU	astronomical unit: approximately the mean Earth-Sun distance
jansky	Jy	Jansky: spectral flux density - 10-26 W/Hz m+2
lightyear	lyr	light year - 9.4607x10+15 m
mag	mag	stellar magnitude

Imperial Units

Name	Abbreviation	Description
cal	cal	thermochemical calorie: pre-SI metric unit of energy
foot	ft	international foot - 1.2x10+1 inch
inch	inch	international inch - 2.54 cm
pound	lb	international avoirdupois pound - 1.6x10+1 oz
mile	mi	international mile - 5.28x10+3 ft
ounce	oz	international avoirdupois ounce
yard	yd	international yard - 3 ft

Others - Engineering

Name	Abbreviation	Description
NoUnits	none	scalar - no units specified
encoder	enc	encoder counts
count	ct	counts as for an encoder or detector
pix	pix	pixel

Usage Examples

Typescript

//declare keyName
const s1: string = 'encoder'

//making 2 keys
const k1 = booleanKey(s1)
const k2 = shortKey('RandomKeyName', 'meter')

//storing a single value
const booleanParam: Parameter<BooleanKey> = k1.set([true])

//storing multiple values
const paramWithShorts1: Parameter<ShortKey> = k2.set([1, 2, 3, 4])

//  default unit is NoUnits
// booleanParam.units === "NoUnits"

//retrieve values from Parameter
const allValues: Array<number> = paramWithShorts1.values

// allValues === Array(1, 2, 3, 4))
// paramWithUnits3.units === "meter")

//default unit for UTCTimeKey is second
const tParam: Parameter<UTCTimeKey> = utcTimeKey('now').set([
  new Date().toUTCString()
])
const defaultTimeUnit: Units = tParam.units //is second