Chandrayan-2 Mission

SwamyG · Post by **SwamyG** » 03 Sep 2019 09:47

First Deorbit of Vikram successful.
_______ From ISRO________
Chandrayaan-2 update: First de-orbiting maneuver
The first de-orbiting maneuver for Chandrayaan-2 spacecraft was performed successfully today (September 03, 2019) beginning at 0850 hrs IST as planned, using the onboard propulsion system. The duration of the maneuver was 4 seconds.

The orbit of Vikram Lander is 104 km x 128 km. Chandrayaan-2 Orbiter continues to orbit the Moon in the existing orbit and both the Orbiter and Lander are healthy.

The next de-orbiting maneuver is scheduled on September 04, 2019 between 0330 - 0430 hrs IST.

Mort Walker · Post by **Mort Walker** » 03 Sep 2019 10:13

Arjun wrote:If there is no live streaming...what is it that Modi and apparently some 60 other kids from cross India specially flown in to Bangalore will be watching live during the landing on the 7th? I presume there must be some facility for regular updates during the last one hour?

It will be live at ISTRAC where they will celebrate the telemetry data. If all goes well, the first image will come some 15 minutes after landing.

Ramesh · Post by **Ramesh** » 03 Sep 2019 11:11

National Geographic Channel is planning to broadcast live. What will be the content, no idea.

SwamyG · Post by **SwamyG** » 03 Sep 2019 11:11

The Chinese were able to take isotopes on their Chang'e 4? But we could not!!! I know reasons were given in the earlier pages of this thread. Hopefully this mission gives us the scientific and political muscle to counter global forces.

Any ways slow and steady is good. I am glad ISRO is so competent and people are so nice. The elephant will always get there unmindful of what people think and say.

SwamyG · Post by **SwamyG** » 03 Sep 2019 12:05

I sent info on the lander and soft landing to a few WA groups of friends and families. It was a mix of women and men, and I got only 2 acknowledgements - both from women. Positive. I guess the average Ram, Ramu and Raju have other important things on their hands.

Ashokk · Post by **Ashokk** » 03 Sep 2019 12:55

Live media coverage of the landing of Chandrayaan-2 on lunar surface

The soft landing of Chandrayaan-2 Vikram lander on lunar surface is scheduled between 1:30 am to 2:30 am on Saturday, September 07, 2019. This will be followed by the Rover roll out between 5:30 am to 6:30 am. A Press Meet with Chairman, ISRO is also being planned between 8:00 am to 9:00 am.

Based on the interest shown by media across the country, ISRO invites accredited media persons to cover this important event live from Satellite Control Centre (SCC) building, ISRO Telemetry Tracking and Command Network (ISTRAC), I cross, I phase, Peenya Industrial Estate, Bangalore – 560 058 (Google Map link https://goo.gl/maps/sHcmDEL8Q6tKVFX39).

Mort Walker · Post by **Mort Walker** » 03 Sep 2019 17:19

SwamyG wrote:The Chinese were able to take isotopes on their Chang'e 4? But we could not!!! I know reasons were given in the earlier pages of this thread. Hopefully this mission gives us the scientific and political muscle to counter global forces.

Any ways slow and steady is good. I am glad ISRO is so competent and people are so nice. The elephant will always get there unmindful of what people think and say.

As said before, landing will be a great feat as the probability is around one out of two. If the landing does not happen, no big deal, the orbiter will still conduct its survey and better luck next time.

Mort Walker · Post by **Mort Walker** » 03 Sep 2019 17:23

SwamyG wrote:I sent info on the lander and soft landing to a few WA groups of friends and families. It was a mix of women and men, and I got only 2 acknowledgements - both from women. Positive. I guess the average Ram, Ramu and Raju have other important things on their hands.

I have too during the World Cup final and no one really responded. Most people don’t care, even so-called educated people.

SwamyG · Post by **SwamyG** » 03 Sep 2019 17:37

Mort Walker wrote:
SwamyG wrote:The Chinese were able to take isotopes on their Chang'e 4? But we could not!!! I know reasons were given in the earlier pages of this thread. Hopefully this mission gives us the scientific and political muscle to counter global forces.

Any ways slow and steady is good. I am glad ISRO is so competent and people are so nice. The elephant will always get there unmindful of what people think and say.
As said before, landing will be a great feat as the probability is around one out of two. If the landing does not happen, no big deal, the orbiter will still conduct its survey and better luck next time.

Yes, landing is the cream at the top. Rover rolling out is the cherry on the top. Cake is the orbiter.

rsingh · Post by **rsingh** » 03 Sep 2019 22:51

I think ladder of lander touches the surface at very steep angle. Rover could simply fall off the ladder. JMT
BTW why there is so much time gap between landing and releasing of rover? Is there any Sat com issue?

juvva · Post by **juvva** » 03 Sep 2019 23:50

rsingh wrote:I think ladder of lander touches the surface at very steep angle. Rover could simply fall off the ladder. JMT
BTW why there is so much time gap between landing and releasing of rover? Is there any Sat com issue?

Maybe they are waiting for the lunar dust (raised during landing) to settle down.

Mort Walker · Post by **Mort Walker** » 04 Sep 2019 00:12

rsingh wrote:I think ladder of lander touches the surface at very steep angle. Rover could simply fall off the ladder. JMT
BTW why there is so much time gap between landing and releasing of rover? Is there any Sat com issue?

After Vikram lands, all data will be analyzed by ISTRAC to make certain health of Vikram and Pragyan are good. That comes first, then analyze the conditions to deploy Pragyan. What if Vikram lands in some crater hole and the ramp can’t be dropped down to deploy pragyan? What if the first pics come back and reveal an alien standing next to Vikram looking on in curiosity? No reason to immediately deploy Pragyan and scare away the ET?

prasannasimha · Post by **prasannasimha** » 04 Sep 2019 00:38

There will be a whole host of system checks before Pragyaan can start its roll out. Remember that Vikram is virtually taking a powered descent and will be virtually dropped from a height of 5 meters and crash to the moon to avoid having a rocket plume distorting the landing site. It will be having crush landing pads to soften the impact etc etc. Now once it lands and the dust settles it will do a system self check to check that all is in order. May also switch on various sensors. Confirm its ability to communicate with the rover and than only open the door and allow Pragyaan to roll out. Prior to rolling out it must ascertain that its wireless communication to the rover is OK, all batteries are fully charged, etc, etc.

Ashokk · Post by **Ashokk** » 04 Sep 2019 02:03

Possibly Pragyaan's battery might need to be warmed up and charged after being exposed to low temperatures during the orbit. Further details from the ISRO research paper here.

F. Wake-up logic
The block schematic of the proposed rover power system conﬁguration is shown in Fig.3. The wake-up of the rover happens, with closure of the switch S1. The activation of wake-up is based on satisfying the following conditions.

•Rover temperature ≥0◦C. All of the generated solar array output, before wake-up, is used for heating of the equipment bay of the Rover. This, together with direct sun load helps in building up the rover temperature after an extreme cold lunar night.

•The solar panel generation can support a load of 1A at 18V or the battery can provide a current of 1A at 18V. Before the wake-up, health of the battery(the battery is connected in discharge mode to the bus during this time) or the generation from solar panel is veriﬁed by connecting the bus to a heater load of ≈1A, for around 20ms. If bus voltage is maintained above 18V, with the 1A load, wake-up is carried out. This check ensures that, after the closure of S1, bus can support the minimum bus load of 1A.

gashish · Post by **gashish** » 04 Sep 2019 04:40

Chandrayaan-2 update: Second de-orbiting maneuver successful

The orbit of Vikram Lander is 35 km x 101 km.

Chandrayaan-2 Orbiter continues to orbit the Moon in an orbit of 96 km x 125 km.

Varoon Shekhar · Post by **Varoon Shekhar** » 04 Sep 2019 04:54

^
Going really smoothly, this was a major de-boost. Wonder if the 800 N engines would have been used for this, or only the thrusters. And the 800 N LAMs operate for the powered descent starting Saturday morning.

Was the satellite's orbit adjusted to 96km x 125km for efficiency and optimised performance of the payloads?

juvva · Post by **juvva** » 04 Sep 2019 07:26

35 km x 101 km -achieved
36 km x110 km -planned

SSSalvi · Post by **SSSalvi** » 04 Sep 2019 08:36

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 in the beginning they may not want to take chances.

Risky and adventurous events maybe near end.

At the lunar evening they might have plans to explore the northern inner slopes of some craters nearby which have never seen the sunshine because even if it slips, the most experiments would have been conducted before it's accidental death.

juvva · Post by **juvva** » 04 Sep 2019 09:20

Chandrayaan 2's Planned Landing Most Complex In ISRO History: Ex-Chairman

https://www.ndtv.com/india-news/chandra ... an-2095061

Saral · Post by **Saral** » 04 Sep 2019 10:30

"On soft-landing on the Moon, he said its something like flying saucers coming in hovering on the top and then slowly descending, as in science fiction."

Question: How were these capabilities tested/mocked on earth?

This article describes NASA testing of LM in the Apollo program.

http://www.thespacereview.com/article/2462/1

Amber G. · Post by **Amber G.** » 04 Sep 2019 10:48

Vikram's landing sites Manzinus C and Simplelius N craters align with the orbit at the landing time on Sep 7th at around 2 am. A perfect polar orbit and a perfect alignment. Everything looks as good as planned.

Amber G. · Post by **Amber G.** » 04 Sep 2019 10:53

Here is journey so far. (The orbits are polar - projecting in 2-dim).

Amber G. · Post by **Amber G.** » 04 Sep 2019 11:31

SwamyG wrote:The Chinese were able to take isotopes on their Chang'e 4? But we could not!!! I know reasons were given in the earlier pages of this thread. Hopefully this mission gives us the scientific and political muscle to counter global forces.

Any ways slow and steady is good. I am glad ISRO is so competent and people are so nice. The elephant will always get there unmindful of what people think and say.

For perspective - The radioisotopes for Chang 4 (and others) were used only for heating, and not to supply power. The total weight needed for RHU was about 40 grams (including all the shields etc). Pretty small. It would have simplified quite a bit in design too (no heating circuits/systems etc). (Slightly OT: There is a proposed new method to produce Pu-238 that could make production more efficient and (*much* cheaper) than traditional method so ISRO may help us to innovate in another field - At present Pu-238 costs about few thousands dollars per gram - Good news is India/DAE (unlike ESA which used Am-241) does have domestic supply of Pu238)

SwamyG · Post by **SwamyG** » 04 Sep 2019 12:17

1. So are the considerations to heat; a political/administrative task of taking isotopes up in the air (somebody mentioned ISRO did not make a request), or is it scientific/engineering one (essentially a weight issue)?

2. 35 x 101KM is nearly a circular orbit, curious why it is not "perfect" circular orbit? After all the orbiter is powered, unlike the natural planets and moons orbiting Sun and planets respectively.

juvva · Post by **juvva** » 04 Sep 2019 15:19

suryag wrote:Dhoti shiver started for me

It is dilbu time now........we need him badly, to calm our nerves.

Mort Walker · Post by **Mort Walker** » 04 Sep 2019 17:38

SwamyG wrote:1. So are the considerations to heat; a political/administrative task of taking isotopes up in the air (somebody mentioned ISRO did not make a request), or is it scientific/engineering one (essentially a weight issue)?

2. 35 x 101KM is nearly a circular orbit, curious why it is not "perfect" circular orbit? After all the orbiter is powered, unlike the natural planets and moons orbiting Sun and planets respectively.

Let Vikram land first, then we can discuss RTG. There is a lot which can go wrong come 7 September. Success rates are around 50%.

It is an elliptical orbit in polar configuration as AmberG. pointed out above. The moon’s gravity is not uniform. It’s mass is lumpy and a shallow circular orbit would require more use of thrusters to keep it in position.

Vivek K · Post by **Vivek K** » 04 Sep 2019 19:11

This entire mission has been awesome. ISRO has demonstrated it is ready for interstellar exploration (RTG heater or not). Mort is correct. We need to watch the next steps - lander and rover. Every inch the lander moves from here on - there will be a lot of learning. The orbiter is already in position.

Varoon Shekhar · Post by **Varoon Shekhar** » 04 Sep 2019 20:35

It's definitely been awesome, virtually flawless thus far. One sour note- in all the determination and passion of ISRO to ensure the success of the mission, other missions appear to have pushed by the wayside. At this juncture, only one post Chandrayaan launch is confirmed before the new calendar year, that of Cartosat-3. Not a word about a Gslv Mark 2 launch, another Gslv Mark 3 with Gsat-20, Pslv with Risat 1A, not even the SSLV-1 certain by year end. In 2018, ISRO was speaking very confidently about one launch per month in 2019. We know they are not going to meet that target.

Don't complain here.
Use the other thread.

disha · Post by **disha** » 04 Sep 2019 21:38

^Monsoons? We can take the monthly launch capability to the Indian space page.

Landing at South Pole of Moon will be the first time ever for any nation. It is by far more complex than landing at Moon's equator which is relatively flat.

I am praying that Chandrayan-2 finds ice on moon and we would be able to explain how the ice came to be there.

SSSalvi · Post by **SSSalvi** » 04 Sep 2019 21:57

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

As schedule published pre- ch2 launch

Amber G. · Post by **Amber G.** » 04 Sep 2019 22:05

35 x 101KM is nearly a circular orbit, curious why it is not "perfect" circular orbit? After all the orbiter is powered, unlike the natural planets and moons orbiting Sun and planets respectively

Virtually all orbits are *not* circular, moon's orbit around earth (and Earth's orbit around sun) is elliptical. But Vikram's orbit is as perfect as it gets. This perfect orbit was planned in advance by our best scientists and is executed perfectly. This is to put Vikram in an exact place where it can soft land. Truly Wow!
(Click to link below to see how perfect the orbit is)

(There is an old joke about Indian parents who, when their child gets 99% in a test, ask the child "what happened to 1 point?"

- In this case Chandrayaan is getting 100%!!!)

. So are the considerations to heat; a political/administrative task of taking isotopes up in the air (somebody mentioned ISRO did not make a request), or is it scientific/engineering one (essentially a weight issue)?

As pointed out, this could be discussed in other thread but let us keep this dhaga for CY2 celebration. (Short answer: No, it is not weight issue, ISRO did not think it needed/wanted it. We will use it when our antriksh-yatris land on moon.)
***
Meanwhile, sankara's animation has been updated with latest data. Here one can see the perfect orbit.. how it is aligned with the two landing sites etc.. Please click on the link
https://twitter.com/i/status/1168614557427699712

RonyKJ · Post by **RonyKJ** » 04 Sep 2019 22:22

The simple answer to why there is no RTG heater on Pragyan is that we haven't yet developed an RTG heater.

A Nandy · Post by **A Nandy** » 05 Sep 2019 00:11

https://swarajyamag.com/science/explain ... ns-surface

The lander will use on-board devices such as the Hazard Detection and Avoidance system (HDA) to study the landing site for safety and accuracy. Various sensors will feed critical data, related to velocity, acceleration, orientation etc. into the HDA system for it to make the required changes in trajectory if and when required.

Using the data obtained, the lander will autonomously determine the trajectory it will have to take to get to its pre-determined landing site.

The breaking engines will fire until the lander is just few meters above the selected landing spot. When the lander is right above (by some accounts, 2 meters above) the landing spot, the engines will be cut-off. The lander will fall freely to the lunar surface and its legs will absorb the shock.

If the engines are not cut off before the lander reaches the lunar surface, its exhaust plumes will kick up Moon dust. The dust, along with the backflow of exhaust gases from the engines can, among other things, harm parts of the lander, including the sensors and scientific instruments it is carrying.

The lander is expected to touch down between two craters, Manzinus C and Simpelius N, about 70 degrees south of the lunar equator. If it manages to soft-land at this point sometime around 7 September, it would have reached closer to the moon’s south pole (around 600 km away) than any previous mission.

Four hours after its soft landing, the lander’s ramp will open, making a passage for rover Pragyaan to drive off to the lunar surface to carry out experiments.

2 meters sounds like quite a drop, though probably not for the moon.

Probable landing site:
https://www.google.com/moon/#lat=-68.44 ... =simpelius

Mort Walker · Post by **Mort Walker** » 05 Sep 2019 00:26

Vikram weight on earth with fuel is 1471 Kg. The weight on the moon is 1/6 of the earth. Vikram is about 245 Kg weight on the moon. You can then calculate the forces on each leg of the lander whether it is dropped from 2m or 5m.

ramana · Post by **ramana** » 05 Sep 2019 01:47

Do that for having raised the issue.
And AmberG will correct your answer.
Our folks have forgotten basic physics.

Vivek K · Post by **Vivek K** » 05 Sep 2019 02:38

correct me if I am wrong -

On earth -
Mass of Vikram = 1471 kg
Weight of Vikram = 1471 kg x 9.81 m/s2 = 14.43 kN

On Moon
Mass of Vikram = 1471 kg
Weight of Vikram = 1471 kg x 1.622 m/s2 = 2.39 kN

For 2 m fall : Favg = 937/4 =234 N per leg.

For 5 m fall: Favg = 2389/4 = 597 N per leg.

Mort Walker · Post by **Mort Walker** » 05 Sep 2019 05:07

Vivek K wrote:correct me if I am wrong -

On earth -
Mass of Vikram = 1471 kg
Weight of Vikram = 1471 kg x 9.81 m/s2 = 14.43 kN

On Moon
Mass of Vikram = 1471 kg
Weight of Vikram = 1471 kg x 1.622 m/s2 = 2.39 kN

For 2 m fall : Favg = 937/4 =234 N per leg.

For 5 m fall: Favg = 2389/4 = 597 N per leg.

The 1471 Kg is launch mass of Vikram including fuel. I don't know if that also includes the launch mass of Pragyan, but for the moment, let's assume so. When we say launch mass, that is the weight of Vikram on the earth in Kg. At least that is the way I understand it. The weight of Vikram on the moon will be less the fuel expended.

Mort Walker · Post by **Mort Walker** » 05 Sep 2019 05:23

Not directly related, but a simulation of a Vyomnaut walking on the moon.

RonyKJ · Post by **RonyKJ** » 05 Sep 2019 05:52

It depends on the deformation distance assumed. We need to know how much the shocks on the legs move or how much the legs dig into the ground.

Energy of an object weighing 1471 kg falling from hover at 1.622 m/s2 over a distance of 2 meters is given by:
E = mgh = 1471 x 1.622 x 2 kgm2/s2 (Joules) = 4772

If deformation distance is assumed to be 20 cm or 0.2 m
Impact force = 2mgh/s where s is deformation distance = 2 x 4772 / 0.2 = 48 kN

This is distributed over 4 legs if it lands on a level surface, so each leg experiences 12 kN

juvva · Post by **juvva** » 05 Sep 2019 08:05

I remember reading somewhere ( need to dig up the source), that the landing strategy is now changed. The engine in the center will be on and firing all the way to touch down(no free fall).