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

Note

The set of supported Units will be modified as more required Units will be discovered.

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
nanometer nm nanometers 10-9 m
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

Time units

Name Abbreviation Description
tai tai TAI Time unit
utc utc UTC Time unit

Usage Examples

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

//making 2 keys
const k1 = booleanKey(s1)
const k2 = shortKey('RandomKeyName', Units.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 utc
const tParam: Parameter<UTCTimeKey> = utcTimeKey('now').set([UTCTime.now()])
const defaultTimeUnit: Units = tParam.units //is utc