Chandrayan-2 Mission

Mort Walker · Post by **Mort Walker** » 10 Sep 2019 20:43

Vayutuvan wrote:
Mort Walker wrote: antilog(-141/10) = 7.94E-15 mW or 7.94E-18 Watts.
antilog(x) is e^x. that said ~1.0e-18 is noise. double calculations in a 64 bit computer consider numerical zero to be 1e-16 or less unless the computations are done in double double, I.e. 128 but.

When talking about power the assumption is base 10. These power levels are routinely detected and used. They are probably using some double or quadruple precision method. I dont’t know, but dinosaurs like myself use decibels because it’s easier to work with smaller numbers in my little brain.

Vayutuvan · Post by **Vayutuvan** » 10 Sep 2019 20:55

SSSalvi wrote:
Pitch, Roll and Yaw are not degrees of freedom.

They are related LOCALLY to the reference body describing its state ( Orientation ) of movement .. not to global frame.

you are absolutely correct.

that said, modeling becomes easier in local reference frame which is most convenient for local geometry - Cartesian, cylindrical, or spherical.

Added to that, local reference frames are covinient when one has to deal with materials that have orthographic or unisotropic properties.

when one is dealing with nonlinear materials or large displacements, properties are dependent on the state, which is easy to express in the said six DOF.

that is the reason why most engineers neither have a need for tensors nor are they taught in Undergrad. Tensors are for problem formulation mostly or to get analytic solutions where possible.

Vayutuvan · Post by **Vayutuvan** » 10 Sep 2019 20:56

Mort Walker wrote:
Vayutuvan wrote:
antilog(x) is e^x. that said ~1.0e-18 is noise. double calculations in a 64 bit computer consider numerical zero to be 1e-16 or less unless the computations are done in double double, I.e. 128 but.
When talking about power the assumption is base 10. These power levels are routinely detected and used. They are probably using some double or quadruple precision method. I dont’t know, but dinosaurs like myself use decibels because it’s easier to work with smaller numbers in my little brain.

thanks. Probably they have special ASICS doing 256 bit/512 bit/1024 bit DFTs or other transforms for filtering. Signal processing computations have to be done online and control system computations are (hard) realtime.

Haridas · Post by **Haridas** » 10 Sep 2019 21:12

SSSalvi wrote:
2. With a 30 footer , the monn's radiation ( Sun Noise reflected by whole Moon disc ) is in the range of -106 to -108 dbm on Full Moon day. So what was seen as -114dbm etc is the radiation noise ... not signal. It is about halfway between Full Moon and Amavasya.

Beg to differ, carrier can be dug up even below noise floor, by synchronous detection. I was surprised doing a job for CEL rail axal sensor characterization back in 1982. Similar to GPS signal that is way below white noise floor.

Haridas · Post by **Haridas** » 10 Sep 2019 21:16

Mort Walker wrote:
Haridas wrote: No sir.
It corresponds to power inputted into the radio receiver input by the the receiver's high gain dish antenna.
It depends if you measure prior to down conversion, as you said, or the IF power. It's not clear from DSN.

It's a radios rating, always corresponding to signal level seen at its input. In older radios the AGC bias is a rough measure of input signals carrier power

Mort Walker · Post by **Mort Walker** » 10 Sep 2019 21:39

Haridas wrote:
Mort Walker wrote:
It depends if you measure prior to down conversion, as you said, or the IF power. It's not clear from DSN.
It's a radios rating, always corresponding to signal level seen at its input. In older radios the AGC bias is a rough measure of input signals carrier power

True, but newer digital receivers use the magnitude of the quadrature to determine power based on a scaled reference signal. This reference could be the IF power or a known value from a signal generator. I assume DSN is doing that when we see power values fluctuating in “real time” on their website.

For DSN, an AGC would only add noise. They should be able to discern high level and low level power easily in down conversion.

Mort Walker · Post by **Mort Walker** » 10 Sep 2019 21:47

Haridas wrote:
SSSalvi wrote:
2. With a 30 footer , the monn's radiation ( Sun Noise reflected by whole Moon disc ) is in the range of -106 to -108 dbm on Full Moon day. So what was seen as -114dbm etc is the radiation noise ... not signal. It is about halfway between Full Moon and Amavasya.
Beg to differ, carrier can be dug up even below noise floor, by synchronous detection. I was surprised doing a job for CEL rail axal sensor characterization back in 1982. Similar to GPS signal that is way below white noise floor.

Correct. See my post earlier. The DSN is much like a real time spectrum analyzer.

UlanBatori · Post by **UlanBatori** » 10 Sep 2019 23:10

-116dB inside a narrow band, is HUGE compared to -106dB for whole spectrum. Look at it this way: -116dB is 10dB or a factor of 100 lower. That means the power in that one narrow band, is 1/100 of the power in the WHOLE spectrum. If the spectrum is on the order of 10^9 Hz to 10^15 Hz (WAG), and the narrow band is only say 1^9 Hz (1 GHz) around the 8.41GHz (which is VERY wide), that means the narrow band is only 1/10^6 of the spectrum, if the spectrum were uniform (which it is not, I know, but the microwave band has much less than the average power of the spectrum: Most of the solar spectrum AFAIK is centered about Green (500 nanometers wavelength) while microwave is well beyond the Infrared, at around 35 millimeters. Spectrum is pretty low there, the Moon does not look red. IOW, in 1-millionth of the spectrum, you have MORE than 1/100th of the whole power! IOW, 10,000 times the average, per Binori madarssa, maybe 1,732,000 times the background microwave in that part of the spectrum. So yes, they can see it with a narrow-band analyzer plus a notch filter.

I assume nothing found yet. Photos published? No updates in past 24 hours seen on Googlestan

prasannasimha · Post by **prasannasimha** » 10 Sep 2019 23:28

JayS wrote:
prasannasimha wrote:The small thrusters are 25 N ones
From the paper that ramana gave link to:

Chandrayaan-2 Lander will employ a clustered configuration of four 800N engines along with 50N attitude control
thrusters placed at the bottom of spacecraft, to decelerate the spacecraft for braking and soft landing on lunar surface

My error the 25 N thrusters were for the orbiter and 50 for the lander

Varoon Shekhar · Post by **Varoon Shekhar** » 11 Sep 2019 00:21

Prasanna, for how long did the fine braking work, when the communication link was lost with 2 minutes to go, had the fine braking already functioned for some time? Can the precise time be determined from what is known now?

ArjunPandit · Post by **ArjunPandit** » 11 Sep 2019 00:29

Mort Walker wrote:
Haridas wrote: Beg to differ, carrier can be dug up even below noise floor, by synchronous detection. I was surprised doing a job for CEL rail axal sensor characterization back in 1982. Similar to GPS signal that is way below white noise floor.
Correct. See my post earlier. The DSN is much like a real time spectrum analyzer.

very noob pooch..UBji please dont bury me for this..but why can't astrosat work the same? its receivers dont have that capability or it is not positioned?

Mort Walker · Post by **Mort Walker** » 11 Sep 2019 01:02

ArjunPandit wrote:
Mort Walker wrote:
Correct. See my post earlier. The DSN is much like a real time spectrum analyzer.
very noob pooch..UBji please dont bury me for this..but why can't astrosat work the same? its receivers dont have that capability or it is not positioned?

AFIK, Astrosat doesn’t have S band capability. It is more for X band signals.

ArjunPandit · Post by **ArjunPandit** » 11 Sep 2019 01:04

^^thanks I was also searching for Indian DSN, it does have S band capability. Will we be able to connect with IDSN in night? or there also we have some issues. Wiki says it was used for CY1

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

Mort Walker · Post by **Mort Walker** » 11 Sep 2019 01:23

^^^India’s DSN has already been used for CY2.

Ashokk · Post by **Ashokk** » 11 Sep 2019 01:52

One of the DSN antennas in Madrid is being used for transmitting data towards the lander at 1 kb/sec @ 11kW. Data also being received...

UlanBatori · Post by **UlanBatori** » 11 Sep 2019 01:53

No idea about who AstroSat is, sorry. (I don't bury anyone for anything... just gently place the banana peel of simple logic in the path of snooty ppl as they rush to gratuitous sneering jeehad with nose up in the hawa etc. )

Speaking of things on which I have no idea... somewhere above I pointed out why ISRO may have sent a mission where the propulsion system of the last stage had not been flight-tested in space before, AND had to operate maybe at the edge of the performance/instability envelope (speculation, of course). I noted that the mission payload was at the absolute edge of what the launcher could carry, so they just added on a spectacularly ambitious Moon science mission to what could have been justified solely as a launcher test plus maybe putting a comsat at GEO.

One way to justify another such mission quickly, would be to put ion engines on the LEO-Lunar Orbit segment, take 6 months to coast along, and even have a chance to test the final stage thrusters during the 6 months. This might provide the way to have more payload mass, meaning bigger/more final stage thrusters that can come to the Fine Braking stage more gradually, and not push anything in the Fine Braking stage. Because of the gravity variations etc, perhaps the fine braking stage cannot be done any differently to reduce risk.i.e., ion engines may not be able to decelerate the lander smoothly and gradually. I wouldn't know.

But suppose in addition to the main Bailgadi with the Science Package, one could consider a second lander with a repair / reporter robot? Use the Jaspreet Mark 2020 design (ball) to reduce risk there. Bounce/roll surface propulsion can beat the heck out of the 1cm/sec speed of the Bailgadis used to-date. Name it after the Hon. Pagla, given the shape. xLand that first, and welcome the main lander on a subsequent orbit?

This would have enough new and spectacular aspects to make it much more than just a CY-2B. Of course, yes, OT, bliss to phorgive and ignore onlee.

The HUGE dangers of space operations are in the Earth Launch and in the landing/re-entry phases, which are all done in a mode suitable only to military missions, Olympic Ski Jump/Luge and missiles. A more gradual and assured way has to be found. Of course, jet airliners have the same problem, but enough crashes have occurred to learn enough to make crashes less likely. Someone has to break through these problems. Maybe run a high school competition to come up with concepts for self-propelling inflatable cricket balls.

UlanBatori · Post by **UlanBatori** » 11 Sep 2019 02:03

Economic Times:

scientists had also deliberated whether there were “gaps in the understanding of the lunar atmosphere” closer to its surface. Such data is not available in the public domain and the space agencies of Russia, the US and China — that have landed probes on the moon — do not share this information, the scientist said.

Read more at:
//economictimes.indiatimes.com/articleshow/71046231.cms?from=mdr&utm_source=contentofinterest&utm_medium=text&utm_campaign=cppst

Did the electrostatically charged dust short out the comm I wonder? Moon has developed its own ~~Planetary~~ Heavenly Defense System IED-mubarak? Or is there a radio blackout in that region? The lander was traveling too slowly to form a shock in front, I believe.

suryag · Post by **suryag** » 11 Sep 2019 02:13

Ashokk wrote:One of the DSN antennas in Madrid is being used for transmitting data towards the lander at 1 kb/sec @ 11kW. Data also being received...

Snapshot sir

IndraD · Post by **IndraD** » 11 Sep 2019 02:15

Ashokk wrote:One of the DSN antennas in Madrid is being used for transmitting data towards the lander at 1 kb/sec @ 11kW. Data also being received...

what is source of this information pls

Ashokk · Post by **Ashokk** » 11 Sep 2019 02:26

suryag wrote:
Ashokk wrote:One of the DSN antennas in Madrid is being used for transmitting data towards the lander at 1 kb/sec @ 11kW. Data also being received...
Snapshot sir

The session ended before I could take a snapshot, it was on 2.2 GHz for a couple of min max.

Ashokk · Post by **Ashokk** » 11 Sep 2019 02:27

IndraD wrote:
Ashokk wrote:One of the DSN antennas in Madrid is being used for transmitting data towards the lander at 1 kb/sec @ 11kW. Data also being received...
what is source of this information pls

Deep Space Network Now

IndraD · Post by **IndraD** » 11 Sep 2019 02:57

how do we know message is being received by dsn> sorry for naive Q !

Ashokk · Post by **Ashokk** » 11 Sep 2019 03:08

IndraD wrote:how do we know message is being received by dsn> sorry for naive Q !

We won't know the message, we can just observer if data is being sent and/or received. If the lander is sending back data consistently then possibly there is still some hope.

UlanBatori · Post by **UlanBatori** » 11 Sep 2019 03:16

If somebody buzzed me continuously at 8AM on a Sundin morning I know what Response Message I would give... Poor thing has been poked and prodded, tested, queried, gawked-at, had to pose with Mantris and Babus, was shaken and stirred, then flung out, then again shaken awake and finally dropped from a height.. Now time to rest. Give it time...

ArjunPandit · Post by **ArjunPandit** » 11 Sep 2019 03:18

UlanBatori wrote:No idea about who AstroSat is, sorry. .

assuming you were serious, which is a big one
https://en.wikipedia.org/wiki/Astrosat

UlanBatori · Post by **UlanBatori** » 11 Sep 2019 03:28

^^ Seriously. Ppl accuse me of being expert on this and that. I am not expert on anything except... PINGREJI!!!!
I had nooo idea. Thanks! Wow. Reminds me of the Virginia Slims cigarette advertisement.

GSLV Mota: We've come a long way, Baby!

A Space Telescope! Can it be accidentally tilted to view the Gravitational Ano-Maly Hasina Atim Bum I wonder. More to the point can it see the bottom of the Moon 70.9 deg. south latitude onlee?

UlanBatori · Post by **UlanBatori** » 11 Sep 2019 03:32

BTW, This is what I wanted to ask: Given that ISRO seems to be really busy, could it be that all those ppl sitting in Mission Control are permanent full-time Mission Controllers?

Like Air Traffic Controllers? I thought they were rocket-scientists pulled out of the machine shop, lorry pool, car pool etc and put in front of a screen with orders to go down a checklist and push keys and take down numbers, while listening to cricket commentary on their head phones.

ArjunPandit · Post by **ArjunPandit** » 11 Sep 2019 03:34

UlanBatori wrote:^^ Seriously. Ppl accuse me of being expert on this and that. I am not expert on anything except... PINGREJI!!!!
I had nooo idea. Thanks! Wow. Reminds me of the Virginia Slims cigarette advertisement.
GSLV Mota: We've come a long way, Baby!
A Space Telescope! Can it be accidentally tilted to view the Gravitational Ano-Maly Hasina Atim Bum I wonder. More to the point can it see the bottom of the Moon 70.9 deg. south latitude onlee?

ok i need to delete the post before you quote it..

disha · Post by **disha** » 11 Sep 2019 03:36

UlanBatori wrote:BTW, This is what I wanted to ask: Given that ISRO seems to be really busy, could it be that all those ppl sitting in Mission Control are permanent full-time Mission Controllers? Like Air Traffic Controllers? I thought they were rocket-scientists pulled out of the machine shop, lorry pool, car pool etc and put in front of a screen with orders to go down a checklist and push keys and take down numbers, while listening to cricket commentary on their head phones.

UB'ji, it is not humour if it crosses a limit. The above comes in that category. The above is a non-question since the answer to it has no material impact.

UlanBatori · Post by **UlanBatori** » 11 Sep 2019 04:09

disha wrote:
UlanBatori wrote:BTW, This is what I wanted to ask: Given that ISRO seems to be really busy, could it be that all those ppl sitting in Mission Control are permanent full-time Mission Controllers? Like Air Traffic Controllers? I thought they were rocket-scientists pulled out of the machine shop, lorry pool, car pool etc and put in front of a screen with orders to go down a checklist and push keys and take down numbers, while listening to cricket commentary on their head phones.
UB'ji, it is not humour if it crosses a limit. The above comes in that category. The above is a non-question since the answer to it has no material impact.

Sorry, it is a serious question. I do not see why anyone should get offended, but apologies if they choose to be that prickly, because I do not have the sensitivity to see why. Certainly no disrespect intended. Anyone who works for ISRO is by definition a "Rocket scientist" to the outside world. Remember Kaleem Khawaja the Sultan of the NRI-SAHI etc? IIT-KGP grad, his job was in the construction dept which built the small buildings and machine rooms and pakistans at a NASA Center. He was called a NASA Scientist. If he was that, then so is every ISRO employee a Rocket Scientist. If you work at Boeing at the security office checking vehicle license numbers, you are a Boeing employee, and that 787 is yours as much as it is that of the VP in a suit sitting in a tower in Chicago flipping PPT charts. In fact the security guard is much closer to reality than the VP is. Fully deserving of the Pride, which the VP probably has none.

If there is only like 1 launch every year, I would ask people all over the organization to step in and do Mission Control. If I have one launch every month, then there is enough work to keep them busy as full-time specialist Controllers.

This has a huge impact on the economics of space operations: the primary cost of space ops is the salaries, not the hardware or fuel or lease of the facilities. IOW it takes a "standing army" of expert people to get a rocket up there and back. You cannot just hire and fire them like software companies do: their expertise is very special.

An outfit like Kennedy Space Center has launches practically every week ( guessing) with numerous launch pads and numerous customers. So they will have full-time controller army, I suppose. But I had no idea that ISRO had enough launches to occupy so many controllers. Apparently I was wrong: ISRO seems to have many more launches than what makes the newspapers in Mongolia.

Also, are the controllers shared between defence and civilian missions? Except for the duration (so far), the processes are pretty similar, so the skill-sets should be similar down to the expert who scans all system reports in a flash (no joke that!) and updates "Situation Naarmal".

So how does ISRO operate? Trained specialist controllers, who have to be taught each different mission? Or do the scientists, engineers, machinists, everyone, get trained for mission control? Each has its advantages and disadvantages.

Specifically now: when something goes wrong, and is not in the Mission Control Manuals, what happens? Do the scientist-turned controllers get to solve the problem? Or does it just get tossed back into the labs while the expert mission controllers wait?

Please answer if you can. Yes, it is a serious question.

SriKumar · Post by **SriKumar** » 11 Sep 2019 04:53

UlanBatori wrote:BTW, This is what I wanted to ask: Given that ISRO seems to be really busy, could it be that all those ppl sitting in Mission Control are permanent full-time Mission Controllers? Like Air Traffic Controllers? I thought they were rocket-scientists pulled out of the machine shop, lorry pool, car pool etc and put in front of a screen with orders to go down a checklist and push keys and take down numbers, while listening to cricket commentary on their head phones.

Ah...Kaleem Kawaja....brings back memories of a brief email exchange I had with him, about Godhra, 2002 (

). Very active on that front. No idea he built buildings at NASA. About mission control, correct me if I am wrong but most of the time most of them dont do anything other than watch the screen and that's it (so I dont even know why they would need to push keys). For unusual missions like Mangalyaan and chandrayaan where human intevention is a part of the task (orbit raising maneuvers and then things beyond that) yes, there is a lot of human intervention built in by design. But for regular PSLV and GSLV launches, I thought every thing was programmed, and if things do not go per program, then another program watching the primary program detects it and stops the first program and all other programs that makes the rocket go. As far as I know, for routine launches (PSLV, GSLV) the one place where human intervention is applied 'on the spot' is the Range Safety officer who says 'command issued'...something you dont want to hear. The rocket explodes after that. There were 2 aborted launches in the last 2 years...both were fuel leaks I believe. That might have been partial human intervention....loss of pressure would have been the software red-flagging it (not human). But once it takes off, I think that's it....willing to be corrected. (As for trouble-shooting...I dont know. I am assuming the ones who did the original design, wrote the navigation plan, software; wrote image recognition software etc get pulled in, that stuff is too detailed. I dont know for a fact but I am betting that not all the critical work goes on in Mission Control. Data feeds can be sent anywhere; and for the critical stuff the guys monitoring they need some peace around them to focus on the task. Having cameras flying around, VIPs, kids, applause etc. ....does not seem conducive to a heavy-duty task.)

ArjunPandit · Post by **ArjunPandit** » 11 Sep 2019 05:11

Not that I want to do bean counting, but using NASA DSN would also cost money

UlanBatori · Post by **UlanBatori** » 11 Sep 2019 06:06

SriKumarji, thx. But there must be a specific function for every terminal/screen and keyboard. Most of them had notepads and were doing some work on them, also comparing notes and looking at each other's screens on rare occasions. So I would think it is division of labor: If there are X subsystems to monitor with data feeds, maybe have 2X Mission Controllers - or maybe the # of subsystems is so large that each controller monitors 5.
That requires very specific training and instructions. The headsets must be giving some overall status updates that are different from the ones blaring on the TV programs.

Yes, the TV cameras and noise etc must be VERY distracting. I won't suggest that the 10 ppl who actually control it sit in a sweaty dingy basement in a hardened shelter under the launchpad and all these 300 nicely-dressed ppl with the fine chairs are there strictly for the PR, because Disha will have me killed.

Some had mikes in front of them. I have heard that in some launches, every subsystem person has to verbally confirm "OK 2 Go" or "10-4, Roger!" or some such, b4 the Launch Director gives the launch command, but today that might all be automated down to a Red or Green LED.
But I am still curious whether these are strictly specialist Controllers, or do they go back next morning to their cubicle/desk in individual departments?

What happens, say, right now if one were to go look at Mission Control? Desks empty? Or people still hunched over every screen?

Dileep · Post by **Dileep** » 11 Sep 2019 06:58

Remember the story of "pilot and dog"?

I think most of the folk sitting there are the ones responsible for the individual functions/modules, sitting there watching like a bunch of parents on the sidelines of kids league. Those are simply ringside seats with full visibility to all data (unlike us armchair mission specialists who see only TV coverage). Most of the 'check-out' had been automatic from late 90s (I had an ex ISRO colleague who used to do manual check-out, and then built the microcontroller system that automated it). So, very little real time action. It is all kirket watching onlee. The notepad is to quickly calculate duckworth-lewis equation.

Except the range safety officer. He sure will have the red button!

Dileep · Post by **Dileep** » 11 Sep 2019 06:59

BTW, Happy Onam to all! King Maveli did visit moon to the ailing munna for sure.

UlanBatori · Post by **UlanBatori** » 11 Sep 2019 07:01

Unless they can call an alert, there is no reason to give each person a screen and a nice chair, right? it's like putting a trailer full of Oracle Operators behind each Tesal self-driving car. I wonder if Dr. Sivan could call in through the headphones:

Station #338B: What is the highest value in the 3rd column pls?

67, Saar. Ishant Sharma has given away 67 runs in 5 overs onlee!

SSSalvi · Post by **SSSalvi** » 11 Sep 2019 07:10

The boys,girls and oldies who are sitting at consoles are the same guys who designed and tested and qualified their respective systems.
There is no separate group dedicated to operations.

And to use the analogy: the knowledge is passed on from generation to generation.... hands on knowledge.

It is an involved knowledge not found even in scientific journals so has to be documented and passed on.
_------
Right now Madrid DSN is attempting contact with lander and next goldstone is lined up for orbiter contact.

Vayutuvan · Post by **Vayutuvan** » 11 Sep 2019 07:11

Ashokk wrote:One of the DSN antennas in Madrid is being used for transmitting data towards the lander at 1 kb/sec @ 11kW. Data also being received...

What is the carrier frequency?

Vayutuvan · Post by **Vayutuvan** » 11 Sep 2019 07:14

UlanBatori wrote: ... AND had to operate maybe at the edge of the performance/instability envelope

That is why Rocket Science is known as "pushing the envelope".

For example, just firing two rockets, hain jee? You need 3 points not colinear to define a plane, 4 points not in a plane, ..., n+1 points not in n-hyperplane, to define n-dimensional space.

UlanBatori · Post by **UlanBatori** » 11 Sep 2019 07:19

SSSalvi wrote:The boys,girls and oldies who are sitting at consoles are the same guys who designed and tested and qualified their respective systems.
There is no separate group dedicated to operations. And to use the analogy: the knowledge is passed on from generation to generation.... hands on knowledge. It is an involved knowledge not found even in scientific journals so has to be documented and passed on.

Fabulous way of operating. Lifecycle attention and care. Some were praying, maybe giving thanks. I mean before the anxious wait started.