Thursday, September 19, 2019

VIKRAM STATUS - 3

It is 17.00 hrs lunar time .....

(Report time: 19.09.2019; 15.00 hrs)
Its going to be another 2-earth days time left, that there will be some amount of light which can soak Vikram's solar panels in bringing life back. Its almost dusk like scene on the moon for Vikram. Once the night kicks in; it has to bear the bone freezing -200C for another 14-earth days.

A sad news from NASA is; their Lunar Reconnaissance Orbiter Camera (LROC) on Sept. 17 imaged the south pole landing site of Vikram lander, "but long shadows in the area may be obscuring the silent lunar explorer" is the statement on their part.

Have a look at the landing site of Vikram (courtesy: NASA)... you need extraordinary skills to be able to spot a flat location. Had the Vikram succeeded in applying breaks to counter the huge forward (orbital) velocity; reaching down to 400-m, ISRO had every other hurdle worked out in the form of a built in Artificial Intelligence by employing a Hazard Detection and Avoidance System (HDAS). As things stand today.... the HDAS had no chances of coming into play.

Vikram landing site            Credit: NASA


This is the time for me as well to throw my hat in the ring..... in predicting what could have been the scenario......

"It could have been malfunctioning of those two diagonal 800-N variable thrust engines which could NOT have delivered the 'THROTTALABLE' performance." Hence the tumble (flip) which could have occurred at 2.0 km altitude, leaving no chance for the built in mechanism to assist in soft landing.


Friday, September 13, 2019

Vikram Status -2 ; Chandrayaan II

Vikram - last contact @ 335-m NOT 2.1-km

13th September, 14.00 hrs IST
As per the Indian Express report (12th Sept), the last signal received from Vikram appears to be from as low altitude as 335-m.
Lets see what could have happened during the 2-phases of breaking in the height range of 18-km to 400-m.
Tapan Mishra, Ex-SAC (Space Application Center) and PRL (Physical Research Laboratory) director, Ahmedabad; distinguished scientist @ ISRO-HQ; has written in his facebook account the details of Vikram landing of 15-minutes. In his smooth flow of words; he has thrown light on what exactly would happen when Vikram switched from Rough breaking (18-7.4 km) to Fine breaking (7.4-km to 400-m). Apparently, it was a switch-over from 4-cornered retro engines to 2-diagonally opposite engines for the fine breaking phase from 7.4-km to down below upto 400-m. Without mentioning the actual cause of the Vikram incident; he did warn that during the fine breaking the operation of 2-diagonally opposite engines is a pretty involved and tricky procedure. Considering the fact that a less filled fuel tank would "slosh" leading to the exhaust of fuel to these engines and hence would lead to un-even burn. Hence, it will be very difficult to provide a "uniform centrally directed breaking force"; this  is what clearly emerges from that discussion.
Taking a cue from the above explanation; it can be conjectured that:
1. Though the switch-over to 2-engines from 7.4-km and downwards would have occurred.
2. The signal loss at 2.1 km could be due to a tumble; taking the direction of communication (antenna) away and hence the signal loss
3. Best part is: Vikram did sail through 2.1-km to 335-m. If one recalls; it had 3-more milestones below 400-m to accomplish: a. @400-m: hover and activate Hazard Detection and Avoidance sensor b. @100-m: select one of the 2-targeted locations c. @10-m: stop and hover to ensure the point of landing
4. Since, the above 3-milestones are AI-based. There is a very high probability of Vikram making it safely to lunar surface and hence a good news, which could emerge in these couple of days....
Wishing ISRO-team again a very best of luck.

Wednesday, September 11, 2019

Vikram Status : Chandrayaan II

12th September, 2019; 11.00 hrs IST.
Post 7th Sept., 1.55 am; every space enthusiast and an Aam aadmi is seeking the status of Vikram. The resolve and intent shown by ISRO is commendable in tracing down Vikram within 40-hours (roughly). It was an extra-ordinary effort on part of ISRO to employ Imaging IR Spectrograph (IIRS) to pick Vikram. As per ISRO norms; the payloads would be made operational as per the prior determined sequence from their hibernation status. I am sure, the waking up of IIRS is an exception as it provides unprecedented 80-m resolution images.
The palpable pressure on ISRO can also be judged by the fact that they have requested public faith in them as theier best efforts are behind the salvaging efforts of Vikram.
In my view: though ISRO was fully prepared for any eventuality ("15-min terror"); they had to face rude shock of uncertainty as Vikram descended below 3-km. As per the views expressed by anonymous team members; the lack of simulations on Vikram could have been the reason behind unknown situations faced by Vikram.
Lets face it... on moon, you got ambiance (atmosphere) which is 10-orders of magnitude less than what you feel on earth (760 torr of atmosphere). You could never ever simulate these conditions for testing the throttelable retro engine (800-N capacity) lets say. There was no way you could simulate 100s of kmph speeds to test breaking mechanisms. As per one report; even a simple drop of Vikram from an aircraft would have given some handle on testing out the AI behind the Hazard Detection Avoidance Sensor system. Well.... Vikram had not reached that phase at 2.1 km anyway.
So as we have completed 6-earth days out of the 14-available on the moon to perform post Vikram operations....Having spend 4+ years for the Chandrayaan-I; Moon Impact Probe mission time... I can assure every one that Team ISRO is not going to leave any stone un-turned....
Lets wish ISRO....... all the very best....

Monday, September 9, 2019

Fate of VIKRAM lander ; Chandrayaan II


A grab of display panel of Vikram landing @ Bylalu, ISTRAC ; Courtesy: DD
It is just around 60-hrs that the contact of Vikram lander had lost. The support, ISRO got starting from the Prime minister and other ministers is commendable; not to forget the foreign media, NASA and of course millions of Indians who kept themselves awake post mid night and were not able to sleep after the episode. A poem went on to pour the feelings of Vikram mentioning that how hard it was as it had to face the aspirations of 1.2 billion people. While ISRO has been working very hard to get to the bottom of the facts, a 1st statement from Chairman ISRO, was that they have identified the VIKRAM by IR-imager. There are dozens of anonymous opinions by ISRO scientists/engineers coming out to the public domain by media; few 10s by experts all around the globe and innumerable by every other soul; explaining if it had not happened this way, then could it not have happened the other way.

I was the team leader of CHACE payload in Moon Impact Probe of Chandrayaan I; spent 4+ years in VSSC-ISRO and have gone through the grill/drill of ISRO in transforming a commercial instrument into a smart, most sophisticated, highly rugged which sucks a very small amount of power from the main power bus with every nut and washer which has been used was argued quite a few times in its selection of weight, dimension. Having left ISRO post Chandrayaan-I, right now I head the central instruments facility here at the University of Hyderabad. The following discussion is purely based on what has been floating around in the media along with my own personal comments and has nothing to do with ISRO. As I have been doing; I will treat this to be a highly popular level; without compromising the value of message I intend to put across.

Vikram lander showing 4-engines firing; Courtesy : Digit
Vikram took a "power descend" from its intended 30X0 km orbit; basically starting from Perigee point of its earlier orbit and heading towards the intended 71-degree southwards journey. Power descend meaning, Vikram is using its forward orbital velocity of around 1.66 km/s (a whopping ~ 6,000 kmph) for its southward journey while the 4 - (throttelable) retro-engines will be keep on firing against the orbital velocity and hence the net effect of "breaking". As per the reports appearing in the media [WITHOUT ANY AUTHENTICATION]... these were major milestones along its 15-minutes of terror covering 30-km journey in a parabolic trajectory.

1. De-orbit operation : 30-18 km

2. Rough breaking : 18-7.4 km

3. Fine breaking : 7.4km - 400 m  [ Activate Central Retro-engine; Shut off 4-Engines]

4. Hover for 12-s : @ 400-m : [Activate Hazard Detection & Avoidance (HDA)]

5. Hover for 25-s : @ 100-m : Select the target A or B

6. Prepares for touch down: 10m-2m in 13-s

7. Shut down engine : @ 2-m

Free fall from 2-m: [Four wheels are equipped to take the shock of this order]

As the nation and entire world watched; Vikram's path veered during soft breaking [as can been seen on the display panel above] and at 2.1-km altitude the green signal on the display panel disappeared; the gloom prevailed all over the faces was very evident and after span of 20-minutes or so, Chairman, ISRO declared that the data link to Vikram has been lost. It was not only the ISTRAC control center of ISRO at Bylalu, outside Bangalore which dipped in ocean of sorrow, every other Indian who was waiting for that successful moment were completely devastated. On my personal behalf, I kept on reviving the possible scenarios which were possible; also got involved in discussions in my 3-4 Whattsapp groups; in a way taking away the gloom prevailing around. Waited for the following day to head to the TV discussion.

The following day; 2-leading news papers published completely opposite views (quoting anonymous ISRO scientists) on the probable causes of the Vikram incident. While one said that it is the over breaking during the soft landing which could have contributed to skidding effect [aka car] on the Vikram. While the other attributes it to under performance of retro-engines. Many other experts gave their views as widespread as possible.

By noon: ANI news broke the story for the first time, quoting chairman, ISRO that " Vikram has been spotted by IR imager of the Orbiter; later to CNN News18 that the health of the Vikram can not be confirmed."

On the 2nd day of incident; many more stories [speculative/anonymous] appeared....
1. Vikram might have crash landed [either on its side or upside down]
2. Vikram is in one-piece [suggesting no greater damage]
3. Orbiter ORHC camera can detect the damage
4. ISRO would persist contacting Vikram for all the 14-days
5. The chances of revival would fade faster as the time passes by


POSSIBILITIES:

Let's be clear that; when the contact was lost; Vikram, at 2.1-km above was guzzling with the speed of around 200-kmph. Again, as per the newspaper report; the soft breaking operation would involve switching from 4-corner based engines to a single central engine.

Scene-1 [status-1]: Could only be a tumble, due to malfunction of throttelable engine; or the 4-engines. However, the close loop guidance system [CLGS] working properly running through the remaining milestones of 4 - 7 as explained above. Vikram has survived the incident and has landed safely. Also supported by one of the reports that Vikram is in one piece

Scene-2 [status:0] : Lets face it, the 200-kmph is enormous speed. Signal loss means the Vikram has tumbled; so much so that it has not allowed the close loop guidance system [CLGS]  to tackle the situation. Let me just remind you all that CLGS will work only when there are aroun 20+ sensors feeding the input to the computer and then on the decisions were to be followed. Which means, a meager failure of one retro-engine, gyroscope could lead to failure in breaking system. Hence the CLGS not at all getting a chance to run thru the remaining milestones of 4 to 7.

Scene-3: Neither 1 nor 0: There is a very finite possibility that a combination both the above scenerios could lead to system surviving but with a BIG question mark... will it perform the oprations of letting the Pragyan slide out.

My take:
Since communication link snapped before event; believing that the Artificial Intelligence has done its job to its best trained scenario; finding the hardware in one piece (unconfirmed report)....
SCENE-3 APPEARS TO BE MOST PROBABLE....

Lets hope best out of the above three cases and we get to see some ray of hope... Tomorrow...

ALL THE BEST ISRO...... you have done all the humanly possible actions, to quote chairman ISRO.



VIKRAM STATUS - 3

It is 17.00 hrs lunar time ..... (Report time: 19.09.2019; 15.00 hrs) Its going to be another 2-earth days time left, that there will be...