Bharat Rakshak

SSSalvi

1) If the extra thrust tilted the lander from 90 to 180 degrees then it will have more horizontal delta V? 2) can they simulate the effects in hardware-in-loop model on the ground? 3) How did the omni directional antenna lose communications when the lander tilted? 5) Why did the engine produce more...

SSSalvi

Not much light on what exactly went wrong .. but the compounding of problems well summerized. https://frontline.thehindu.com/science-and-technology/article29477285.ece?homepage=true It descended to about 33 km above the moon. As Vikram entered the fine braking phase with only 2 km to go before touch...

SSSalvi

Waiting for the images of shattered DreamLander. Next Lunar day begins midnight bet 4th and 5th Oct. CH2 Orbiter will cover the landing sight between 9th and 10th Oct with good Sunlight. LRO is not a good candidate to image polar areas. It will cover the Landing Site between 16th and 17th Oct .. but...

SSSalvi

There are NO images.... Orbiter orbit does not pass over intended Landing Site.

If it has to image the area then they have to make the ORBITER look across track .. have they planned for that capability vis a vis onboard fuel budget of what they are claiming of 7 years lifetime?

SSSalvi

^ Communication loss is the result of total disorientation of TM antenna aboard Lander due to tumbling of the platform ( Lander itself ). The Landing videos in ISRO publicity materials show that the lander orientation changes from legs in front to legs at bottom. ( PITCH rotation ).During this trans...

SSSalvi

What's the signature? 1) The lander reverse thrusters experienced delta Thrust 2) Lander tumbled in pitch axis leading to the reverse thrusters adding delta V towards moon surface 3) Lander lost communications ---- My money is on either some structural flaw or non-homogeneity of the liquid fuel. In...

SSSalvi

UB
It is a crater of which left and right portions have been cut during stitching

SSSalvi

About current orbit data: ISRO never publishes orbit data. ( State Vector or TLE are the correct terms. ) Celestrak is an authentic source for latest TLE for Earthbound Satellites . It doesn't include CY2 after it entered Moon gravity. For crafts in non-stellar orbits jpl/nasa horizons is the only k...

SSSalvi

Ignore for now ... will post updated @Ramana Here is a closeup of situation. Showing the craters referred by ISRO. ISRO says ( Prior to Launch of CY2 ) the site is 'between' the craters. But the Lander path ( Based on jpl/nasa data base ) and the landing ( CRASHHHHH) site around location marked as 2...

SSSalvi

Stale subject ... stillllllll posting for records: Showing the Lander path while descending ( LO in image below ) and the lander position at 20:19 UTC ( 1:40 IST ). Inset shows thae same situation but in detail. Also shows the ORBITER ground trace and its position when the Lander was lost. I doubt i...

SSSalvi

^
^
After thorough testing & confirmation of logic in C etc, final coding is converted to manually written machine code embedded in Space qualified ROMs/PLAs.

^
Let the thread be live .. why lock?

SSSalvi

What exactly was the landing spot for Lander?

I was using ( much before Launch of GSLV ) -72Lat and 22.5Long based on some source .

Now someone said -70deg ......etc .

Doctor saab any correct info?

SSSalvi

^^^ From same report some useful snippets: ( It seems to have been written before the catastrophe. the moon lander Vikram’s operation from the time it started its journey towards soft landing on the moon on September 7 early morning: “The lander Vikram was horizontal at 30 km altitude at a speed of ...

SSSalvi

Goldstone DSN on with CH2
Orbiter :Tx. 2.05 Ghz. & 7.18 Ghz. Tx Pwr 0.25 kw
Rx. 2.23Ghz

Lander attempt :
Tx Frq 2.1Ghz. Power: around 10Kw

SSSalvi

Not to the extent that the communication would be stopped.
There is always a extra margin of 3 to 4 db to overcome eventuality.. this margin is sufficient to at least a very very feeble hearing of signal by a 30 footer of DSN

SSSalvi

My Take.. albight harsh: This is only a show op ... To show that 'we are trying.' Is it possible that those who have spent years in designing every component and subsystem will not know what has happened at exactly the moment the failure has happened? Ok, identification of exact faulty component or ...

SSSalvi

Right now lander wake up call is still on.
( Kumbjharna can wake up if alive.. Mara hua hoga to kaise uthega? )

SSSalvi

Rx freq from orbiter:2.23Ghz
Rx power :-130 dbm
Data rate : 1 kbps

Other antenna trying for lander:Tx signal
Freq 2.28 GHz
Plain carrier

SSSalvi

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 a...

SSSalvi

Objects which are nearby operate on different freq.
Let's see when DSN starts next operation with orbiter

We have noted lander freq above

SSSalvi

8 GHz is standard allotted freq for satcom and desh had been using it for ages .. for low altitude satellites

SSSalvi

Presently ( 1600 IST ) it is visible to Canberra @ 70deg El Will be visible till India midnight. For Madrid it will rise at around 11PM IST Note : Sat may be visible but station may or may not track depending on operations schedule. ================ ^ ^ There was a reference that we require 6 degree...

SSSalvi

Yes, I guess they're just looking for a carrier. No data is being sent up. In extreamly poor Signal to Noise ratio (SNR) signal (often due to link budget exhaustion) one can reduce the receiver bandwidth to few Hz only, thereby maximizing the SNR to be just above noise floor. It just tells you ther...

SSSalvi

What is 6 axis?

SSSalvi

Right now ( 0820 IST ) Goldstone is transmitting 11 kw @2.1 GHz using ant#24 to CY2. Data rate is not there in status panel.

SSSalvi

General public have seen the tearful faces in this WA ,Twitter,FB age so drawing conclusions about why those tears? Are they croc tears? .. etc. Were there no tears in the absence of these media hypes? Does not one weep when his project fails? Do people not cry when years of mehnat goes waste in a f...

SSSalvi

A good scientific analysis showing that the communication failed at 20:20:01 UT. Those people use telemetry from official telemetry partner. . https://mobile.twitter.com/cgbassa/status/1170055327775109120 Please avoid discussions on comments from others.. let's concentrate on scientific content.

SSSalvi

One of the reasons why communication failed is a mispointing of antenna due to sudden rotation of the yaan... Even before crash.

SSSalvi

Appears to have started tumbling ( could be due to firing or misfiring of one of the thrusters ) and so pushed it into the moon rather than applying elevation force.

------
Bagala has become a commentary terrorist.

SSSalvi

If admin were negative, we would not have known that there is a dilboo.

SSSalvi

Cannot compare two different items which have their own different goals and targets.

Each is called excellent when the job is executed meticulously.

SSSalvi

As an ex insider: Every single step ( like, how to route a cable in a particular way ) is discussed, discussed and discussed in at least 4 5 meetings plus in at least 3 review meetings involving intercenter personnel from various specialities. Views are fought tooth and nail and after meeting same g...

SSSalvi

Rony post ..
Care ... He has computed for Earth.

SSSalvi

Do that for having raised the issue. And AmberG will correct your answer. Our folks have forgotten basic physics. :) Well said! :) BTW Good Morning from Landing site. Seeing first light of day. Waiting to Dilboo the avenger. Last time fellow dropped a heavy missile .. not this time . Dilboo, Help!

SSSalvi

October launches pushed to Nov.
About 4 Pslv and 3 Gslv till December

As schedule published pre- ch2 launch

SSSalvi

Soft landing maneuver will obtain the most detailed images of terrain near landing site ever obtained. Operators may take at least an hour to find the safest first crawl .. avoiding accidental pitfalls like tipping over, facing intense shadows etc and then chart and upload the first trail. At least ...

SSSalvi

Mort Walker wrote: To get the most bandwidth, it might be possible for Vikram to transmit the video data to Chandrayaan and then from there to earth.

Yaan will be visible to rover/lander only for a small part of orbit of yaan.
Moreover the antenna should have been designed for this operation.( Pointing to yaan )

SSSalvi

On a 2nd thought.. they may not release it .. it will expose the proprietory algorithms developed for this and they may not want to make it public at least till some protection ( read patent/publication in scientific community) is in place.

SSSalvi

Basic cause of no video coverage during descent is the antenna pointeing to Earth. If you try to orient the antenna it will create mechanical disturbance confusing the landing decision. But I am sure that they will record the whole video onboard ( for post descent analysis of the decision making pro...

SSSalvi

Lander separated from orbiter. There is media coverage of Chandrayaan-2 lander Landing from 1:30 AM IST onwards on Sept 7 and Pragyan rover rolling out from the lander from 5:30 AM IST. Do we know if images or video will be sent by Vikram during the landing phase? At least a few images prior to lan...

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