Ham receives ISRO Mars Orbiter

Hi Paul,

It’s wonderful that you have made a serious effort to publicly post this (one) data capture and presented it here for queries. This renders credibility to the data AS data (your previous data was on a site that warned it may be fictitious), although there are many questions with respect to the validity of your identification of its source--that is MoM spacecraft orbiting Mars.

Here's a few questions as starters, to let everyone critique this public data.


1) You spectrum flags three separate monochromatic spikes, with limited signal to noise. In the waterfall display(below it), these spikes do not appear at all, despite your superposition of a green line allegedly connecting one with a Doppler shift(in time). Can you kindly explain why we see no evidence of any visible signal features --for any of the spikes--within the waterfall display? Why did you ‘green line’ that one? It is feebly stronger than the other two spikes. Why that one?

2) What transmit power should we assume in the theoretical estimate of received power? You will note that I already showed you that your claimed MoM power received was far below detectable limits for a 3 foot dish, at that channel bandwidth, over that integration time. If you find errors in that estimate, please show us what they are, kindly.

3)Next, your data, again, makes no attempt to demonstrate that you are seeing a celestial source (that is, Mars). This can be shown simply by several on-offs, in azimuth or elevation. Kindly explain why you still have not supplied what amounts to a standard ‘control’ in this observation? It should be very easy to do a simple video showing the dish slewing on, off, and so on, for example. A quick youtube video would suffice.

4)Next, you assert this was done with a 3 ft chicken wire-style dish. I calculate a beamwidth full width half maximum (3 dB points) of approximately 9 degrees at 13.5 cm. That means there is still considerable gain response over at least 20 degrees of solid angle, if not more. Your time of measurement---26 Sept at roughly 19:40 -- is after sunset, and Mars was about 10 degrees above the horizon, according to the star charts on that date in Great Britain (your home). At that time, the beam of your dish has considerable response looking at a 300 degree Kelvin ‘Earth’--you are seeing ground. This should balloon the system temperature and severely degrade the sensitivity of any observation: no observer observes near the horizon with a large beamwidth. Also the noise ‘floor’ has a base dB very close to your previous observation, done at a different elevation at the time of observation. Kindly explain how this is possible.

5)Can you, again, tell us your system temperature at the time of observation?

6)On that dish, how are you supporting it? Horizon viewing requires considerable edge support. Can we get a picture of that?

Let’s start here, and I will provide more questions as needed.

Thanks for following thru, and I am sure we will get to the bottom of whether you detected Mom or not with the equipment you describe.

73
Chip W1YW

 

Hi Paul,

It is fraudulent for you to make a claim that I am your consultant.

Also, you ask us to pay money to see the data. Please explain why we should do this--it is your claim, and thus your obligation to publicly--not privately--make it available.

Shouldn't we assume that you are compensated for said dowload?

I am not. And wouldn't.

73
Chip W1YW

 

Also, I have no way of judging whether M0EYT has sent a recording to me, but I do not accept unsolicited files.

As mentioned, the claim that I am his consultant is fraudulent.You should consider his intentional and knowingly false statement in the context of considering the alleged data and its origin.

I will not pay to look at a recording of this data.

73
Chip W1YW

 

[1] I did not take that claim as anything but a jibe. Anybody else?

[2] The low-speed download was free.

 

Claim [1] I also took as definitely a jibe. Chip is my consultant
[2] yes, it's definitely free.

Oh, hang on. Different consultant. I was thinking of Chip formerly known as Chipmunk, the well known English rapper.

But anyway, now looking forward to seeing Paul's answers as this is fascinating me now, and I keep reading up on the subject matter at hand.

 

"Safari cannot download this file"

...and hangs up on download attempt on Surface... Might be antivirus kicking in.

 

This from ISRO on 09-24-2014:

http://www.isro.org/mars/updates.aspx

But the Southgate ARC article states:

Is there a discrepancy between the two statements that needs explanation?


Further discussion here:

http://www.nasaspaceflight.com/2014/09/draft-indias-mom-spacecraft-arrive-mars/

Another link:

http://www.universetoday.com/114667...t-fires-main-engine-for-mars-orbit-insertion/

IDSN

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

 

Perhaps I should dig out my old Apple iiC?.

W1YW

 

A DSL connection?

 

Hi all except W1YW,

Not sure about the 'publicly posting one FFT' - the twitter feed has had a number of FFT's from MOM posting, a few highlights below;

http://pjm.uhf-satcom.com/twtr/mom_2292980.jpg LGA antenna shortly after launch
http://pjm.uhf-satcom.com/twtr/mom_2298425.jpg LGA antenna shortly after launch
http://pjm.uhf-satcom.com/twtr/mom_2298516.jpg LGA antenna shortly after launch
http://pjm.uhf-satcom.com/twtr/mom_2298411.jpg LGA antenna weak signal

http://pjm.uhf-satcom.com/twtr/mom_150614.jpg - doppler compensated, other LEO signals present
http://pjm.uhf-satcom.com/twtr/mom_200714a.jpg - non compensated

http://pjm.uhf-satcom.com/twtr/mom_210914.jpg
http://pjm.uhf-satcom.com/twtr/mom_210914a.jpg
http://pjm.uhf-satcom.com/twtr/mom_220914.jpg
http://pjm.uhf-satcom.com/twtr/mom_230914.jpg
http://pjm.uhf-satcom.com/twtr/mom_240914.jpg
http://pjm.uhf-satcom.com/twtr/mom_240914a.jpg
http://pjm.uhf-satcom.com/twtr/mom_260914.jpg

BTW "The radio link between the Spacecraft and Earth is now blocked by Mars." - this was during MOI, same thing happened during the MOI phase with the Mars Recon Orbiter, FFT's near the bottom of http://www.uhf-satcom.com/amateurdsn/newmro/ page.

Regards,

Paul M0EYT

P.S. I will ask a US station to verify the S-Band signal at some point in the near future.

 

I think a reasonably prudent person would accept the evidence you have provided. My dilemma is that I can't tell if the condescending hand-waving and posturing we see in post #76 has any validity at all or is just bafflegab. I see nothing there which identifies any error in your data. Question 2 seems irrelevant to what you claim. Question 5 only implies a possible source of error. Question 6 especially seems strange. And it implies no end to the nonsense with

Riiight.

Still wondering if a QSL card can be had from ISRO.

 

Let's go over the link budget again step by step and annotated.

1) 230 watt TWTA on spacecraft = +53.6 dBm.<cite class="_Rm"></cite>

http://www.isro.gov.in/pslv-c25/pdf/pslv-c25-brochure.pdf

The ISRO link confirms the 230 watt TWTA on the spacecraft. A TWTA is a non-linear device, essentially a class C amplifier. There's no reason to back off the power on these devices, so they are run full throttle. The modulation is most likely BPSK, which is just digital phase modulation. I don't see any reason why we can't use 230 watts for the spacecraft transmit power. +53.6 dBm (decibels above a milliwatt) is 10 log (230/.001).

2) 2.2 meter parabolic dish on spacecraft at 2.293 GHz and 60% efficiency = 32.2 dBi gain.

The gain of a parabolic dish is pi squared times the diameter squared divided by the wavelength squared and then multiplied by the feed efficiency.

pi squared = 9.8696
2.2 meters squared = 4.84 meters
13 cm (0.13 meter) squared = 0.0169 meters

9.8696 * 4.84 / 0.0169 = 2826.56 * 0.6 = 1695.936
10 log 1695.936 = 39.294 dB

3) 224637068 km path loss at 2.293 GHz = 266.7 dB.

This is just the Friis equation. 4 pi times the distance divided by the wavelength and then squared.

4 pi = 12.566
distance = 224637068000 meters
wavelength = 0.13 meter

12.566 * 224637068000 / 0.13 = 2.17144e+13
2.17144e+13 squared = 4.71515e+26
10 log 4.71515e+26 = 266.73 dB

In an earlier post, W1YW was concerned about ionospheric losses. The only ionospheric loss at 2.3 GHz is due to scintillation and polarization loss due to the Faraday effect. Scintillation only occurs during geomagnetic storms (or nuclear bomb detonations) and the spacecraft uses circular polarization. Probably no more that 0.5 dB degradation and one of the reasons that the Deep Space Network uses 2.3 GHz in the first place.

4) power level at Earth = 53.6 + 32.2 - 266.7 = -180.9 dBm.

This is just spacecraft power plus spacecraft antenna gain minus path loss.

5) The noise figure of a G4DDK preamp at 2.293 GHz is about 0.3 dB, or a noise temperture of 21K.
average sky temperature at 2.293 GHz is around 20K.
Let's add 79K in feedline loss and say that the system noise temperature is 100K.
The noise floor at 100K and 0.38 Hz bandwidth is -182.8 dBm.

The equation for thermal noise floor is p = kTB
p = noise power
k = Boltzmann's constant = 1.3806488e-23
T = noise temperature
B = bandwidth

1.3806488e-23 * 100 * 0.38 = 5.24646e-22
10 log 5.24646e-22 = -212.8 dB below a watt
-212.8 dBW = -182.8 dBm

In an earlier post, W1YW tries to invoke some form of "sigma" statistics, but the the noise power calculation is already an RMS value. No need for more statistics.

The real magic (and what makes this all possible) is the 0.38 Hertz bandwidth. A modern quad core x86 processor (even though it's marketed as a general purpose processor) is a formidable DSP. An FFT with 0.38 Hertz bandwidth is entirely possible. Welcome to 2014.

The antenna gain for a 1 meter dish is about 25 dB, and because it's homebrew lets reduce that to 20 dB.

So the received power is -180.9 dBm + 20 dB = -160.9 dBm
The thermal noise floor is -182.8 dBm, so the signal to noise ratio is 21.9 dB.

M0EYT is showing signal to noise ratios around 10 to 12 dB, so it fits into the expected link budget.

W1YW is concerned about the noise temperature of Mars and also the noise temperature degradation when the antenna is pointed near the horizon. Since Mars only subtends 5.8 arcsseconds in a 10 degree beamwidth, it contributes nothing to the noise temperature.

Noise temperature degradation due to low pointing angles is real, but it's effect is not overwelming. If we replace the noise temperature of 100K with 300K, it only raises the thermal noise floor to -178.0 dBm, or a 4.8 dB degradation. Still within the link budget.

KC8VWM asked for the physics. The link budget is the physics.

Here's a link from K1JT that recaps all of the above discussion (from the ARRL Handbook).

http://physics.princeton.edu/pulsar/K1JT/EME_2010_Hbk.pdf

 

Let me jump in with a possibly dumb question.

How do we know that signal is from the orbiter, and not some terrestrial source?

 

The K equivalent of G's section 48 of the Wireless Telegraphy Act 2006 is even more onerous, making it unlawful to reveal the mere EXISTENCE of telecommunications heard by anyone who is not the intended recipient that is not amateur, CB or broadcast.

BTW, since in addition to "messages", the WTA 2006 protects the sender & intended recipient of telecommunications, it would appear that to say a signal was received from something & identifying what that something was, is unlawful.

When one properly gets their head around these implementations of Article 37 of the ITU Constitution, the chatter amongst, logs & compiled schedules published by, recordings of signals shared & the various newsletters from a lot of the radio listening community are all unlawful.

Whether the law or the septic troll is more of an arse might make for an interesting discussion.

73, ex-VR2BG/p.

 

I am taking them there Ron...you are spoiling the fun but feel free to join.

The capture shot showing the multiple sat signals in the same waterfall is the clincher....try capturing Mom and two LEOs--coinicidentally in the same small spectrum at S band--within a pencil beam

BTW, did you know that according to this thread, a signal in the presence of thermal noise is detected at the 1 sigma level;-)?

73
Chip W1YW