Space Flashcards
What is declination
Angle in degrees n/s or the celestial equator
What is Greenwich hour angle
Defines position of longitude measured from Greenwich celestial meridian
What is a zenith
Position of a body overhead the observer at 90° (altitude 90°)
What is the local hour angle
The angular measurement from an observers celestial meridian to the celestial meridian of the body
What are Kepler’s laws
The orbit of each planet is an eclipse, with the sun at one of the focal points
The line joining the planet to the sun, known as the radius vector, sweeps out equal area in equal time
When is the earth closest to the sun
Perihelion = 3rd January
When is the earth furthest from the sun
Aphelion = 3rd July
When is the summer solstice
21st June
Sun = 23.5°N
When is the autumnal equinox
21st September
Sun = 0°
When is the winter solstice
21st December
Sun = 23.5°S
When is the spring equinox (vernal)
21st March
Sun = 0°
What is the plane of the ecliptic
The plane of the earths orbit round the sun
What is the angle between the celestial equator and the suns orbit (the obliquity of the ecliptic)
23.5°
What / where is the Tropic of Cancer
23°27’N
Declination of sun at summer solstice
What / where is the Tropic of Capricorn
23°27’S
Declination of sun at winter solstice
Where is the artic circle
66°33’N
What happens with daylight at the artic circle
At summer solstice the suns rays will pass over the North Pole and places north of the artic circle will have continuous daylight
Where is Antarctic circle and what happens in summer solstice
66°33’S
At summer solstice the sun does not rise
When is the minimum rate of change of daylight
Solstices at mid latitudes
Where is the maximum rate of change in daylight
Equinox at mid latitudes
What is the sidereal year
The period between 2 successive conjunctions of the earth, sun and a fixed point in space (365 days 6 hours)
What is the tropical year
Period between 2 successive vernal equinoxes I.e. time taken for one orbit round the sun relative to the first point of Aries
365 days 5 hours 48mine 45.98 seconds
When can / can’t you have a leap year
YES If year is divisible by 4 (1952,1976)
NO if the year is also divisible by 100 (1700,1800,1900)
YES If year is also divisible by 400 (1600,2000)
What is a sidereal day
Period between 2 successive transits of s particular meridian and a fixed point in space. Constant time interval of approximately 23 hours 56.3 mins
What is an apparent solar day
Period between 2 successive transits of the apparent (visible) sun over a particular meridian
Variable time interval caused;
Earths variable speed along ecliptic
Earths movement along its orbit
What is a mean solar day
Constant length 24 hours
What is mean sun
Goes round path of celestial equator
What is apparent sun
Goes round the ecliptic
What is the equation of time
The time difference between apparent sun and mean sun
What are the months when differences between mean and apparent suns Local and mean times are maximum
Feb / November
What sun do we see in the sky
Apparent sun
What shape is the earth
Oblate spheroid
What is the equatorial radius (ER)
- 56 Nm
6377. 47 Km
What is the polar radius (PR)
3431.97 Nm
6356Km
What is the compression ratio
1 in 298
What does 1° of latitude = in distance
60 Nm
What is 1’ of latitude in distance
1nm
What is the circumference of earth
21,600Nm
Or
40,000Km
What is the “perfect sphere radius”
3441nm
What is the icao definition of 1nm
1852m
Where is the length of a Nm the longest
Longest at the poles
What is latitude
Angular distance to a point measured north / south from the equator
What is a parallel or latitude
Line of latitude
What is longitude
Angular distance measured from 0° to 180° east or west from Greenwich meridian to the meridian passing through a point
What is a ante meridian
The opposite meridian to the one referred to
What’s a parallel or latitude
As well as the equator (a great circle) a small circle defining latitude n/s of and parallel to the equator
What is a meridian of longitude
A semi great circle defining longitude from the north to South Pole crossing the equator and all parallels of latitude at 90°
What is great circle
Any circle drawn on earth with centre of earth as centre of its radius
E.g. Meridian / equator
Distance between 2 points on a great circle = shortest distance
What Is a small circle
Any circle drawn on the earths surface whose radius is less than the earths radius
Parallels of latitude, except the equator are small circles
What is a rhumb line
A regularly curved line on the surface of the earth that cuts all meridians at the same angle
Parallels of latitude are both small circles and rhumb lines
What is the shape / curve of a rhumb line
Concave to the nearer Pole
Convex to the equator
What are other names for the Greenwich meridian
Prime meridian
Origin of longitude
Semi-great circle
What is a graticule
Collectively all the line of latitude / longitude
What is the disadvantage of a great circle track
Not the same heading all along
What is the advantage of a great circle track
Shortest distance
