What size of a radio antenna is needed to recieve signals from Mars?

[whitelancer64]

What size of a radio antenna is needed to receive signals from Mars?

I'm wondering if I could have a, say, 2 meter antenna in my backyard and pick up on signals from the probes on and around Mars, or would it need to be much bigger? 10 meters? larger? I know the DSN antennas range from 26-70 meters in diameter, but that can pick up on signals from the Voyagers, and I'm not that ambitious.

[Jim]

Do you realize you will need an X-band receiver for more than $5k?  And then what are you going to do with the signal?

[StarTracker]

First of all, thanks for your interest in the topic, backyard telemetry reception can be exciting (and time-consuming.) My recommendation is to research the various data rates and radiated power (EIRP) from the probes you're interested in and then calculate the required G/T necessary to receive. I think you'll find that Mars is a tall order for the amateur. That said, I've seen people receive the S-Band residual carrier from LRO (orbiting the moon, naturally) with small equipment, but I don't believe I've seen anyone receive the telemetry subcarriers. Trying for that first may be a better first step.

[whitelancer64]

Do you realize you will need an X-band receiver for more than $5k?  And then what are you going to do with the signal?

Let's say I'm a millionaire and I choose to live modestly in a suburban home in order to support my philanthropy, so the price tag is not an issue.

Really, the question is just because I'm not sure how big of a radio antenna is needed to get a signal from Mars.

[avollhar]

it depends on what you are up to:
receiving data/subcarriers: big antenna, cryogenic low noise amplifiers, just like DSN

just detecting the residual carrier: much easier..
http://www.uhf-satcom.com/amateurdsn/

And to Jim: no $5k receiver required.. they used to be a few (400) EUR from Kuhne-Electronic but he has stopped apparently the production. The UHF-Satcom website above however gives some hints to assemble your own amateur-DSN network.

Antenna size can be as little as 6ft, but obviously: bigger is better.

[whitelancer64]

it depends on what you are up to:
receiving data/subcarriers: big antenna, cryogenic low noise amplifiers, just like DSN

just detecting the residual carrier: much easier..
http://www.uhf-satcom.com/amateurdsn/

And to Jim: no $5k receiver required.. they used to be a few (400) EUR from Kuhne-Electronic but he has stopped apparently the production. The UHF-Satcom website above however gives some hints to assemble your own amateur-DSN network.

Antenna size can be as little as 6ft, but obviously: bigger is better.

That's kind of what I thought, it's not necessarily the size of the antenna, but the sensitivity of the equipment you put on it.

[Nomadd]

 It all depends on your receiver sensitivity. DSN receivers are far more sensitive than anything you'll find in your ham radio catalog. The easiest would be the Indian probe, Mangalyaan, which has 230 watt transmitters on a 2.2M antenna. Compared to a GEO satellite, the probe would have about a 26db advantage from higher power and a more directional antenna, but even near opposition, a 60db disadvantage because of the distance. So, with your average VSAT LNB and receiver, you're talking about a 60M or so antenna. The Indians use an 18M antenna, but could probably pick the probe up with an 8M dish at opposition. I'd guess they were using super cooled, ludicrously low noise receivers you're not going to pick up at Walmart.
 Regular satellite receivers aren't exactly X-band. They use simple LNBs to take the signal down to S-band before it leaves the dish. The DSN uses extremely advanced, cryogenically cooled gear than can be 40db more sensitive, or work at 100 times the distance, of most commercial stuff.

[whitelancer64]

It all depends on your receiver sensitivity. DSN receivers are far more sensitive than anything you'll find in your ham radio catalog. The easiest would be the Indian probe, Mangalyaan, which has 230 watt transmitters on a 2.2M antenna. Compared to a GEO satellite, the probe would have about a 26db advantage from higher power and a more directional antenna, but even near opposition, a 60db disadvantage because of the distance. So, with your average VSAT LNB and receiver, you're talking about a 60M or so antenna. The Indians use an 18M antenna, but could probably pick the probe up with an 8M dish at opposition. I'd guess they were using super cooled, ludicrously low noise receivers you're not going to pick up at Walmart.

Hmm. The EAU's Mars orbiter is going to have a 1.5 meter antenna, and the largest antenna at their ground station in Dubai is 11.28 meters, so they may need to invest in a larger antenna, or rent time on a larger antenna elsewhere, to keep in touch with their Mars probe when Mars is further away from the Earth.

[ThereIWas3]

Transmitter power (Watts), transmitter antenna gain (design and size), free-space loss (distance), polarization loss (antenna alignment), receiver antenna gain (design and size), receiver noise figure (temperature), receiver sensitivity (design), bandwidth (modulation technique), error sensitivity (enocding).   All these factors contribute to the reliability of sending information over a distance.  The umbrella term is the Link Budget.

[Nomadd]

It all depends on your receiver sensitivity. DSN receivers are far more sensitive than anything you'll find in your ham radio catalog. The easiest would be the Indian probe, Mangalyaan, which has 230 watt transmitters on a 2.2M antenna. Compared to a GEO satellite, the probe would have about a 26db advantage from higher power and a more directional antenna, but even near opposition, a 60db disadvantage because of the distance. So, with your average VSAT LNB and receiver, you're talking about a 60M or so antenna. The Indians use an 18M antenna, but could probably pick the probe up with an 8M dish at opposition. I'd guess they were using super cooled, ludicrously low noise receivers you're not going to pick up at Walmart.

Hmm. The EAU's Mars orbiter is going to have a 1.5 meter antenna, and the largest antenna at their ground station in Dubai is 11.28 meters, so they may need to invest in a larger antenna, or rent time on a larger antenna elsewhere, to keep in touch with their Mars probe when Mars is further away from the Earth.

I don't really know how much margin the Indian system has or relative performance compared to what the EAU will have. There's not a great difference between 18M and 12M signal wise. The DSN is available for backup, but I imagine it's pretty heavily booked now days.

[whitelancer64]

The DSN is really overdue for an upgrade / expansion. A few more locations, or improving / expanding the current locations, would ease the workload that it currently has to handle.

The UAE would be a reasonable location for another DSN node, it's more or less between Madrid and Canberra.

[pericynthion]

It's a lot easier if you're simply trying to detect the signal, rather than successfully decode telemetry and payload data from it.

[abuzuzu]

Google
Link Budget

How big of an antenna do you need?
It depends upon
transmitter power
transmitter feed line losses
Transmitter antenna size/ gain/aperture
transmitter distance

operating frequency

receiver noise temperature ( ie sensitivity)
receiver antenna size/gain/aperture
signal bandwidth
Receiver gain

receiver sky temperature generally not a problem at x-band unless the Mars is close to the sun in the sky
Receiver antenna noise temperature ( ie how much of an interfering signal from the earth's thermal radio glow gets into the receiver from the antenna back lobes)

required receiver signal to noise ratio for adequate ( ie sufficiently low bit error rate) reception

The link budget formula and background information tells you how to combine the information above in such a way to tell you how well the receiver is working.

Off the top of my head with no calculations-( yes dangerous I know) high end amateur moon bound stations might be good enough to detect the carrier portion of the signal from mars ( if the signal indeed has a carrier) but actual data reception would be a stretch. 

If you are skilled it is actually quite possible for an amateur to build quite a good X-band receiver but i would guess you need at least a 30 foot diameter dish with reflecting surface accuracy good enough for x-band which is asking quite a lot for a home made antenna.   Some amateur radio moonbounce stations have made use of large surplus antennas so with unlimited budget and a good dose of scrounging luck and a lot of skill in building home made microwave communications electronics, you might, just might be able to detect a signal.

Oh and an antenna big enough to work will have a beam narrow enough to require it track mars across the sky so add a tracking and amining system to you list of engineering design tasks.

[LouScheffer]

This question has now been answered experimentally.  An amateur with a 60 cm dish has detected the carrier from at least 3 Mars missions - MRO, UAE's HOPE, and China's  Tianwen-1.

Of course this is just the carrier, which is MUCH easier to detect than the data (by factors of thousands, at least).  Getting a signal strong enough to decode the telemetry from Mars takes DSN level resources.  This is no coincidence, as JPL sets the data rate as fast as possible until even the DSN has minimal margins.  So anything smaller is out of luck.  There are a few exceptions, such as STEREO.  Here the orbit has brought it quite close to Earth, and the signal is strong enough for amateurs to decode the telemetry.

[LouScheffer]

Nowadays (2023) almost everything needed for X-band reception can be purchased on the open market.  Take a look at the block diagram that has been used to detect Mars missions.  Total cost would be $5000 or so.

The only differences between this and what the DSN uses are (a) giant antennas, and (b) cryogenic front ends.  But the cryo amps are commercially available and indeed are what ESA uses.  So the only real difference between what a sophisticated amateur could do and the DSN is the giant antennas.