"Jim Lux" napisal w wiadomosci
...
On 11/7/2011 1:14 AM, Szczepan Bialek wrote:
"The first observations of cosmic radio emission were made by the
American
engineer Karl G. Jansky in 1932, while studying thunderstorm radio
disturbances at a frequency of 20.5 MHz (14.6 m). He discovered radio
emission of unknown origin, which varied within a 24-hour period. Later
he
identified the source of this radiation to be in the direction of the
centre
of our Galaxy. From: http://encyclozine.com/science/astronomy/radio

I understand that the frequency "varied within a 24-hour period". It is
the
"diurnal effect".
And what about the 365 days period (annual effect)?
S*



You mean when earth is generally heading "towards" the galactic center vs
when earth is heading "away" from the galactic center?

Yes. But on the Earth orbit are places when this speed is 0.5 km/s (only
rotation) or 30 km/s. (orbital speed).

People doing deep space navigation deal with this all the time, since
navigation is done by measuring the frequency of the received signal from
the spacecraft. There's nothing special about it. spacecraft on some
heliocentric trajectory, Earth on a different heliocentric trajectory.

Like the Earth and Mars.

Measure frequency shift, they use to determine spacecraft trajectory by
applying (mostly) Newtonian physics (you do have to use relativistic
corrections to get the last gnat's eyelash of precision).

They confirm the diurnal changings in the frequency. But what with the
annual?

Since you only get to measure in one direction, you have to make
assumptions about what's going on in the other directions, (e.g. cross
range), which can lead to disasters (Mars Climate Orbiter, most recently).

You can do various forms of VLBI and DeltaDOR to get some cross range
information, but nothing as good as what you're getting for range (where
velocity and range are measured to mm/s and cm sorts of accuracy)

Naw are the spacecraft at distances almost like stars. They are not on
heliocentric trajectory.

So I repeat my question:
" I have found the link:
http://chaos.swarthmore.edu/courses/...er_Anomaly.pdf

""It is also possible to infer the position in the sky of a
spacecraft from the Doppler data. This is accomplished by

examining the diurnal variation imparted to the Doppler shift

by the Earth's rotation. As the ground station rotates underneath

a spacecraft, the Doppler shift is modulated by a sinusoid."

Here they confirm the diurnal variation in the frequency.

Probably in this paper is also the answer for my question: "And what about
the 365 days period (annual variation in the frequency)?
Unfortunately I am not an expert in radio. Do you know the answer?

S*