Amateur station hears Mars Orbiter at 45 million miles

[VO1ONE]

This week the Mars-Net e-mail list reported that Paul Marsh, an amateur observer, has detected Mars Reconnaissance Orbiter at X band at a range of 45 million miles from Earth.

The MRO transmits on Deep Space Network channel 32 which is 8439.444444 MHz.
By the time that reaches Earth, due to doppler the frequency has dropped to around 8439.031 MHz. The MRO has a 3 meter diameter dish antenna driven by a 100 Watt X-band TWTA to transmit signals to Earth. The signal coming in our direction is of the order of 4.2 mega watts of RF.

The signal was clearly visible in the FFT display of an SDR-14 software radio, and was just audible in SSB bandwidth of a communications receiver. The signal was consistently about 6 to 8 dB above the noise floor.
More details can seen at:
http://www.uhf-satcom.com/mro



Thanks to Joe, KM1P, the Mars-net list, and
Uhf-satcom.com for the above information

 

[Stargazer]

Wow, thats pretty interesting, I wonder how far one can transmit a signal that can be picked up here on earth. I know that would depend on the type of frequency and how powerful it is and the distance.

 

[VO1ONE]

Wow, thats pretty interesting, I wonder how far one can transmit a signal that can be picked up here on earth. I know that would depend on the type of frequency and how powerful it is and the distance.

Well, NASA still communicates on a daily basis with both of the Voyager spacecraft, which are both billions of miles away from Earth. In fact, Voyager 1 is so far away that it takes nearly 13 hours for a signal to reach it or come back from it. That's quite the delay!

http://voyager.jpl.nasa.gov/news/profiles_dsn.html

What makes this Mars orbiter case special is that a ham, a private individual, was able to pick it up the signal using homebrew and off the shelf equipment. This is the furthest signal any private individual has been able to pick up on their own and the first time its been done. This makes me wonder that if hams are able to build such sensitive downconverters and get such sensitive receivers that they can pick up a signal from Mars on 8Ghz with just a 1m dish, how come we can't get better LNB's and receivers for DBS services that can pick up a signal a fraction of the distance through a heavy rain or snowstorm

 

[charper1]

I am no expert, but would claim:

1. the differences in freq used
2. costs; trying to keep standard end user gear under the $50 mark

 

[VO1ONE]

I am no expert, but would claim:

1. the differences in freq used
2. costs; trying to keep standard end user gear under the $50 mark

I don't find 8GHz all that different from 12GHz. Atmospheric absorption is about the same, and actually that size dish would provide more gain at 12GHz than 8GHz. I have no problem with having the standard, mass produced, boxed with every system el cheapo LNB and receiver, however I think there should be a choice. If there's people out there who don't mind spending a bit extra to have superior reception, there should be someone out there to cater towards them. There's a lot of people who buy broadcast quality stuff for other things electronic as it is.

 

[Stargazer]

You would think that there would be premium products available on the market for DBS just as there is for other products in this area, as VO1ONE mentions above.

 

[VO1ONE]

You would think that there would be premium products available on the market for DBS just as there is for other products in this area, as VO1ONE mentions above.

I thought a little more about this after I replied and I got to thinking about how C and Ku LNB's came in various qualities when I remembered the Invacom QPH-031. While it isn't strictly a DBS LNB, it is probably the best DBS LNB out there. The Invacom boasts a noise figure of 0.3dB, and it's been difficult for me to find a published noise figure for a standard DBS LNB, but the Terk Triple LNB for DirecTV I've read had a noise figure of 1.1dB with a goal of 0.9dB!! There's still nothing I could think of as far as premium receiver products, and it'd be nice if Invacom could come up with a DBS only LNB with those kinds of specs.

http://www.invacom.com/products/qph_031.htm

 

[Stargazer]

Maybe the larger dishes need a better lnbf with a lower noise figure because of how much more interference they are receiving with the large dish.

 

[ClickRich]

Those reading this thread from the UK might be interested to know that they can hear from amateur in question, Paul Marsh, first hand at this free event presented by the Institute of Electrical Engineering:

"45 Million Miles from Earth

In this, the first of the 2006 programme of IEE Lectures in Bournemouth, Radio Ham Paul Marsh describes how he built and used a home made receiver to sucessfully recieve signals from NASA's Mars Reconnaissance Orbiter transmitting in X-band at a staggering range of 45 million miles from Earth. As NASA's New Horizons' mission to Pluto gets underway, for how long can amateurs keep pace with the space race?

Speaker: Paul Marsh, IBM and keen Radio Ham
Venue: Allsebrook Lecture Theatre, Bournemouth University
Date and Time: Tea/Coffee from 6:30pm. Presentation from 7pm, Thursday 2nd March 2006
For further details, go to http://www.iee.org/events/event/2A684783-F3FB-1A06-8A2032FA6B60B44D&i=1
"

 

[KE4EST]

Thats Cool