What is the highest radio frequency used for radio astronomy?

On 30 Aug 2007 15:03:23 GMT, Margo Schulter
wrote:

A frequency of 3438 GHz, with a wavelength a bit shorter than
100 microns, would thus be about an order of magnitude higher
in frequency than the top of the EHF range. While I'm not sure
if there's a specific technical name for this range (analogous
to the various categories of radio waves like EHF), my first
layperson's guess would be that it could be considered very
far infrared (that is, far from the visual spectrum and close
to radio).

They are called submillimeter waves, and represent the transition
between what is widely accepted as "radio" and what is widely accepted
as "optical".

IMO the best way to categorize EM bands is by the nature of the
equipment we use to measure energy in those bands. Submillimeter
radiation is detected using special receivers which combine optical-like
sensors (bolometers) and radio-like sensors (heterodyne receivers and
tuned antennas). I think its best to simply consider the range from
about one millimeter to 1/10 millimeter as "submillimeter", neither
radio nor optical (IR).

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Peter Webb wrote:

"Margo Schulter" wrote in message
...
In sci.astro.amateur gwatts wrote:

Radium wrote:
Hi:

What is the highest radio frequency used for radio astronomy?

According to the link below, it is 3438 GHz:

http://books.nap.edu/openbook.php?re...=11719&page=11

Is 3438 GHz the highest radio frequency used for radio astronomy?

If you read on a little farther you'll find
'blurring the distinction between radio astronomy and infrared
astronomy.'

So where do you want to draw the line between radio astronomy and
infrared astronomy? There's you're answer.

Hi, Radium, gwatts, and all.

I'd agree that the real question here may be where to draw the line
between radio and infrared, and thus between radio astronomy and
infrared astronomy.

What I learned about 40 years ago was that while the line wasn't
a clear one, the shortest or highest-frequency range of radio waves
traditionally placed in that classification were "millimeter waves"
with a wavelength of 1-10mm. Given that the speed of light, c, is
very close to 3 x 10^10 centimeters per second, so that a 1 cm or
10mm wave would have a frequency of around 30 Gz, this category
(also known as Extremely High Frequency or EHF) has a 30-300GHz
range.

A frequency of 3438 GHz, with a wavelength a bit shorter than
100 microns, would thus be about an order of magnitude higher
in frequency than the top of the EHF range. While I'm not sure
if there's a specific technical name for this range (analogous
to the various categories of radio waves like EHF), my first
layperson's guess would be that it could be considered very
far infrared (that is, far from the visual spectrum and close
to radio).

It's interesting question how radio and infrared astronomy are
distinguished: mainly by the nature of the waves, or also by
the apparatus used. I'd like to to learn more of this myself.

Again, I'd emphasize that in giving the range for EHF, I'm not
saying that anything above 300 GHz wouldn't be considered radio,
only mentioning this category as an example of what was
traditionally considered near the top of the radio spectrum.

Maybe Laura or others could comment more expertly on this.

Most appreciatively,

Margo Schulter

Lat. 38.566 Long. -121.430


So its your contention that the atmosphere is transparent all the way up
from microwaves to IR?

She didnt say anything at all about this. Why are you "contending"
contenacity contumaciously?

In article om,
laura halliday wrote:

The usual agreement is that it's radio astronomy when the
incoming signals are electronically detected (e.g. diodes) and
processed. It's optical/infrared astronomy when the incoming
signals are measured by a bolometer or other non-electronic
means. There is, naturally, some crossover.

Given today's CCD chips which indeed are electronic devices, does that
mean todays optical telescopes, with CCD chips which detect light
electronically, have become radio telescopes?

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

In article ,
Chris L Peterson wrote:

IMO the best way to categorize EM bands is by the nature of the
equipment we use to measure energy in those bands. Submillimeter
radiation is detected using special receivers which combine optical-like
sensors (bolometers) and radio-like sensors (heterodyne receivers and
tuned antennas). I think its best to simply consider the range from
about one millimeter to 1/10 millimeter as "submillimeter", neither
radio nor optical (IR).

Or perhaps we could consider that wavelength band both "optical" and
"radio", since radiation at those wavelengths probably can be detected
both with radio and with optical equipment.

And if one wants to decide on some single wavelength limit between
"radio" and "optical", 0.3 millimeter appears to be a good choice
since it resides near the middle of this "submillimeter" band. This
corresponds to a frequency of one TeraHertz.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

Paul Schlyter wrote:


And if one wants to decide on some single wavelength limit
between "radio" and "optical", 0.3 millimeter appears to be a
good choice since it resides near the middle of this
"submillimeter" band. This corresponds to a frequency of one
TeraHertz.

And in fact, e-m radiation at and around that frequency is often
called Terahertz radiation, or Terahertz waves, or T-rays, etc.
More specifically, from 300 GHz to 3 THz is the Terahertz band.
This terminology seems to be used more in non-astronomical
fields.

http://en.wikipedia.org/wiki/Terahertz

--
Dan Tilque

In article ,
Paul Schlyter wrote:

That's a little illogical. It's like considering a frequency slightly
above 300 kHz to belong to "the Megahertz band" ....

Seems logical to me. Anything above 316kHz is nearer to 1MHz than to
100kHz.

-- Richard

--
"Consideration shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.

In article ,
Dan Tilque wrote:
Paul Schlyter wrote:


And if one wants to decide on some single wavelength limit
between "radio" and "optical", 0.3 millimeter appears to be a
good choice since it resides near the middle of this
"submillimeter" band. This corresponds to a frequency of one
TeraHertz.

And in fact, e-m radiation at and around that frequency is often
called Terahertz radiation, or Terahertz waves, or T-rays, etc.
More specifically, from 300 GHz to 3 THz is the Terahertz band.
This terminology seems to be used more in non-astronomical
fields.

http://en.wikipedia.org/wiki/Terahertz

That's a little illogical. It's like considering a frequency slightly
above 300 kHz to belong to "the Megahertz band" ....


--
Dan Tilque




--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

In article ,
Richard Tobin wrote:
In article ,
Paul Schlyter wrote:

That's a little illogical. It's like considering a frequency slightly
above 300 kHz to belong to "the Megahertz band" ....

Seems logical to me. Anything above 316kHz is nearer to 1MHz than to
100kHz.

There's a difference between "the Megahertz band" and "the One Megahertz
band". The former can be interpreted as the band from 1 MHz to 1 GHz
for instance, instead of your interpretation from 0.316 to 3.16 MHz....

-- Richard

--
"Consideration shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.


--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

On Fri, 31 Aug 2007 12:13:05 GMT, (Paul Schlyter) wrote:

That's a little illogical. It's like considering a frequency slightly
above 300 kHz to belong to "the Megahertz band" ....

No, it's _more_ logical. It's having arbitrary names for various regions
of the EM spectrum that isn't entirely logical.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Aug 30, 12:33 am, Radium wrote:
Hi:

What is the highest radio frequency used for radio astronomy?

According to the link below, it is 3438 GHz:

http://books.nap.edu/openbook.php?re...=11719&page=11

Is 3438 GHz the highest radio frequency used for radio astronomy?

Thanks,

Radium
For obtaining eye candy that's entirely outside of our physical reach,
and for the most part having been getting further away as we speak,
the 3.438 THz might be fine and dandy for accomplishing that spendy
look-see which can't possibly benefit humanity or that of our badly
failing environment.

Much above 0.1 THz is where such photons if transmitted from Earth
simply do not reflect unless the target offers a nifty array of
parabolic dishes, or of some other artificial reflective surface.
Outside of our magnetosphere, such as within our moon's L1, is where X
band of 8 ~ 12.5 GHz or possibly as great as Ka Band of 26.5 ~ 40 GHz
might become interesting and/or essential if future space travel is to
avoid those nasty bits and pieces of debris that'll otherwise clean
your clock upon encountering such, with C Band of 4 ~ 8 GHz being a
little better off for those slightly larger targets and perhaps best
of all S Band of 2 ~ 4 GHz offering a compromise that'll still yield
more than sufficient image resolution of a given planet or moon, along
with offering a darn good reflective signal to noise ratio.

However, if the potential target is the least bit intelligent worthy,
as many should be, as such why not use a blue~violet laser cannon, UV-
a, or possibly good old X-rays or even gamma ?

Though gravity can be directly measured, of what we can't manage thus
far is the two-way frequency applications of utilizing said
gravitons. Perhaps there again, the mutual gravity nullification zone
of our moon's L1 could allow for the limited use of gravitons, and
this alternative might become better yet once we've relocated that
moon to Earth's L1.
- Brad Guth