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Author Topic: Feasibility of making 2 way contacts to a space ship on trajectory to Mars?  (Read 7856 times)
AG1LE
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« on: March 13, 2013, 07:19:27 PM »

How feasible would it be to work a ham radio station on a space ship on trajectory to Mars and back?

Spending 500 days in a space capsule might go faster if you have ham radios with you, see this article:
http://www.space.com/19981-private-mars-mission-married-2018.html

Has anybody thought of this and what kind of station would you need in the space capsule and on earth?

I guess stations with EME capability might be able to pull this off  Smiley

73
AG1LE
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KO4MA
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« Reply #1 on: March 14, 2013, 12:44:32 PM »

After a week or so, the delay is going to get real annoying  Grin
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WB5ITT
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« Reply #2 on: March 15, 2013, 11:37:36 PM »

True, just at the moon there is a 4-5 second delay one way....at Mars, its a 12 minute delay one way....packet or a digital mode would be best...voice comm would not be very feasible...which really complicates the landing sequence.....mission control would not know if the landing was successful until after it happened....but that 7 min entry into the Martian atmosphere are know as the 7 minutes of terror...with the robots, if we lose the telemetry, its gone...on manned mission, its possible the screams of terror, etc would be heard...after it happened....still, I would chance it..the biggest problem is GETTING there..cosmic rays and other issues may make a flight to Mars highly unsafe for decades to come...the moon was a pond jump...Mars is the ocean voyage..in a dingy
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AF6WL
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« Reply #3 on: March 16, 2013, 12:06:37 AM »

Brilliant question:

"I've just picked up a fault in the AE35 unit. It's going to go 100% failure in 72 hours."
..... "Roger your plan to go EVA and replace Alpha-Echo three-five unit prior to faliure."

I think the store forwarding of messages will be the way to go - well done Mr Clarke.

How much ERP will be needed to give them enough bandwidth to run Netflix to pass the time  Cry
« Last Edit: March 16, 2013, 12:11:36 AM by AF6WL » Logged
W6RMK
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« Reply #4 on: March 16, 2013, 08:32:42 AM »

How feasible would it be to work a ham radio station on a space ship on trajectory to Mars and back?
not too hard from a technical standpoint..
The problem is that once you get very far away (the moon is 1 second away), you want to probably move towards a more "messaging" rather than "conversing" mode. 
 
Quote
Has anybody thought of this and what kind of station would you need in the space capsule and on earth?

I guess stations with EME capability might be able to pull this off  Smiley

Easier than EME.. EME is a two way path with 1/r^4 loss.  Of course, once you get to twice as far as the moon, you're matching EME.  While you can have W5UN's array on the ground, you don't get that on your spacecraft, so...

You want to go higher in frequency for a variety of reasons.   Today, with readily available components and such, the 10.5 GHz band is a sweet spot. Parts are still inexpensive, test gear isn't all that pricey since it's <18GHz.  A 1-2 meter antenna gives you a lot of gain at 10 GHz, and is still "pointable".

There's a fairly active amateur DSN community that regularly receives signals from spacecraft at lunar distances.



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W6RMK
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« Reply #5 on: March 16, 2013, 08:38:40 AM »

True, just at the moon there is a 4-5 second delay one way
actually, more like 1 second. Moon is about 300,000 km away and speed of light is about 300,000 km/sec.

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....at Mars, its a 12 minute delay one way...

Rough numbers.. Mars is 1.5AU from sun, we're 1 AU. If you recall, it takes a bit more than 8 minutes for light from the sun to get to Earth.  So when Mars is closest (0.5 AU) it takes 4 minutes, when Mars is farthest (2.5 AU) it takes 20 minutes.
Quote
.packet or a digital mode would be best...voice comm would not be very feasible...which really complicates the landing sequence.....mission control would not know if the landing was successful until after it happened....but that 7 min entry into the Martian atmosphere are know as the 7 minutes of terror...with the robots, if we lose the telemetry, its gone...on manned mission, its possible the screams of terror, etc would be heard...after it happened....still, I would chance it..the biggest problem is GETTING there..cosmic rays and other issues may make a flight to Mars highly unsafe for decades to come...the moon was a pond jump...Mars is the ocean voyage..in a dingy
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W6RMK
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« Reply #6 on: March 16, 2013, 08:51:24 AM »

Brilliant question:

"I've just picked up a fault in the AE35 unit. It's going to go 100% failure in 72 hours."
..... "Roger your plan to go EVA and replace Alpha-Echo three-five unit prior to faliure."

I think the store forwarding of messages will be the way to go - well done Mr Clarke.

How much ERP will be needed to give them enough bandwidth to run Netflix to pass the time  Cry

Funny you should ask... This is the kind of thing that folks at JPL figure out every day.  We send several Mbps  (which would be enough for Netflix) back from Mars from MRO.. about 100W into a 3 meter antenna at 8.45 GHz.  This gives about 66 dBW EIRP (4 Megawatts).
http://ipnpr.jpl.nasa.gov/progress_report/42-168/168F.pdfgives some measurements for Ka-band (32 GHz).. about 70 dBW EIRP, using a smaller amplifier

The multimegabit rate is into a 34m antenna on the ground, I believe, although it might be the 70m  (1:4 difference rates between the two).

Going the other way, from ground to earth, is easier. The noise figure on the spacecraft isn't as good as the cryogenic receiver on the ground, but it's easy to get 10s of kW transmitter power on the ground.   So, at least at Mars, streaming Netflix, Hulu, or Youtube to the astronauts is not a problem. (except perhaps for licensing and region restrictions<grin>)

Now, I will grant you that a 34 meter antenna is a big bigger than the average ham might have in their backyard, but there are people who have big antennas (Jamesburg dish, Bochum, etc.)  and there are a LOT of 6-20 meter dishes around which could easily be pressed into service for, say, kilobits/second.
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W2RWJ
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« Reply #7 on: March 23, 2013, 05:41:31 PM »

Now, I will grant you that a 34 meter antenna is a big bigger than the average ham might have in their backyard, but there are people who have big antennas (Jamesburg dish, Bochum, etc.)  and there are a LOT of 6-20 meter dishes around which could easily be pressed into service for, say, kilobits/second.

18.2 meter.  Being repaired by and operated by, of all things, a  bunch of amateur radio operators.  Who would have thought....

http://infoage.org/exhibits/ocean-monmouth-amateur-radio-club/space-sentry-tlm-18





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N6JSX
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« Reply #8 on: March 27, 2013, 03:05:52 PM »

The modulation mode needs to be picked smartly as well as required ERP-Power/band. Here is where digital FM using Manchester (self correcting) type code is needed to minimize solar interference to obtain the best clarity in the smallest bandwidth yielding the most power out.

Mars HAM comm's will take some serious ground equipment to allow the space craft to keep the size/weight down/reasonable to add HAM OPs!

Here is where I suggest parroting established NASA Comm methods and pick near HAM bands for the distance and power required for reliable comm's.

Next question is of NASA big RX dishes - can/will add a HAM RX antenna interfaced to the internet so all on Earth could listen into Mars HAMComm's (and as an emergency comm alternate backup). This would cut half our personal HAM station costs if we can tap into NASA. 
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W6RMK
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« Reply #9 on: March 27, 2013, 09:37:47 PM »

The modulation mode needs to be picked smartly as well as required ERP-Power/band. Here is where digital FM using Manchester (self correcting) type code is needed to minimize solar interference to obtain the best clarity in the smallest bandwidth yielding the most power out.
Why FM at all?  Go with something simple and proven, like BPSK. If I were building it, I would start with BPSK using a fairly fast PN spreading code (say, 1-10 Mchip/second), and then modulate my low rate data on top of that.  There's a lot of off the shelf hardware/software to acquire the PN codes (e.g. GPS receivers do it), and that makes it a lot easier on frequency control (which is challenging with Doppler and all).  The Space Network (TDRS) uses a similar scheme with spreading codes at about 3 Mchip/second.

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Mars HAM comm's will take some serious ground equipment to allow the space craft to keep the size/weight down/reasonable to add HAM OPs!
There's a project going on now at JPL to build a deep space cube sat (INSPIRE). The radio design is adaptable to ham bands, and fits in <1U, and should work with ground stations in the <10 meter class.  It's using standard CCSDS modulation schemes and is DSN compatible.  Since the core of the radio is a FPGA, implementing some other modulation scheme is a matter of writing the software.

There's an off the shelf implementation for the Space Network modulations, including the PN spread modes, that fits in a 3 million gate Virtex II available from NASA Glenn Research Center. (if you're a US Person.. export control is always an issue, even for hams).
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Here is where I suggest parroting established NASA Comm methods and pick near HAM bands for the distance and power required for reliable comm's.
Not necessarily copy what NASA does.  Remember that legacy support is important to NASA, and a lot of what NASA does is based on decisions made on the basis of hardware that was available a long time ago. We just stay with it because it works, not necessarily because it is what you would find best if you were starting today.
Quote
Next question is of NASA big RX dishes - can/will add a HAM RX antenna interfaced to the internet so all on Earth could listen into Mars HAMComm's (and as an emergency comm alternate backup). This would cut half our personal HAM station costs if we can tap into NASA. 
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W9GB
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« Reply #10 on: April 18, 2013, 12:33:46 PM »

Quote from: AG1LE
How feasible would it be to work a ham radio station on a space ship on trajectory to Mars and back?
This was the intention (Earth to Mars communications) of the AMSAT-DL Phase 5 :
 P5A Mission, first proposed in 2002.
http://www.ticket-to-mars.org/

An essential technical element of the Mars P5A mission is the ground station for supervising and controlling the Mars bound probe. The 20 meter parabolic antenna at the Bochum observatory (IUZ) was refurbished and reactivated.
The facility, now operated by AMSAT-DL has already proven its capability through the reception of NASA and ESA probes like Mars Express, the Saturn probe Cassini and the comet probe Rosetta.
In the spring of 2006 a team from AMSAT-DL even received signals from the American space probe Voyager 1 at a total distance of approximately 14.7 billion kilometers.
==
The P5A Mission proposal was turned down for ESA funding last year.

AMSAT-DL web page
http://www.amsat-dl.org/

Wikipedia (DL) entry on P5A
http://de.wikipedia.org/wiki/P5A
« Last Edit: April 18, 2013, 12:39:23 PM by W9GB » Logged
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