Chandrayan-2 Mission

[KJo]

[Mort Walker]

All systems ready to go.

July 14, 2019

The launch countdown of GSLV MkIII-M1/Chandrayaan-2 commenced today at 0651 Hrs IST. The launch is scheduled at 0251Hrs IST on July 15th.

Republic TV will be carrying it live.

[prasannasimha]

^ Small correction Republic TC will be relaying Doordarshan's feed.

[A Nandy]

And I hope they suppress the commentary using a banal words detector

UH25 (fuel) filling of liquid core stage (L110) of #GSLVMkIII-M1 completed.
Updates will follow..

[Pratyush]

This is the first ISRO launch in a long time that I am excited about.

[Varoon Shekhar]

Nice to be in India at this very important and exciting event! Watching all the TV channels while staying at the Grand by GRT hotels, you can feel the buzz. Hope all goes well! I'm even a bit apprehensive about the huge weight of the composite payload, 3.8 tonnes that's the heaviest object ever loften into space by an Indian vehicle. Ah, it should go well. All the best, ISRO!

[Gagan]

Night launch !!!
So the visuals will be short
Is it overcast or clear skies over Sriharikota or chennai?

[SSridhar]

There is a 90% chance of rain for a parched Chennai by 11:30 tonight and 45% by 2:30. But, K.Sivan has already said rains won't dampen the launch.

[Kakarat]

Chennai is partially cloudy now
Unfortunately i wont be attending this launch as my registration had some issues and did not complete, even then i was planning to watch from the lake side but that too is ruled out due to some personal issues

[Katare]

Why are they launching at night? Got delayed to monsoon season so can’t really help overcast weather....

[Singha]

maybe there is a certain position of earth and moon they need to align with for most efficient slighshot injection into lunar transfer path.

[Katare]

Night launch !!!
So the visuals will be short
Is it overcast or clear skies over Sriharikota or chennai?

No Saar one might think so but if you ever wanted to see mythical 8th wonder of the world see a night launch of a rocket. Absolutely amazing visuals and for much much longer. It really looks like those cheesy space paintings. Shooting stars and stray galaxies, awara little clouds and what not. Hope they have good telescopic lenses and good cameraman.

[Singha]

from space.com

[Singha]

so instead of circularing a highly elliptic launch orbit (for regular GSO sats) this time it will make the ellipse major axis longer & longer and then finally escape into the lunar transfer path. then reverse on other side to make ellipse into a circle before lander detaches.

it will be a real coup, and a 'chetawani' if we can do this nose to tail.

I wish I could be a fly on the wall right next to the 1st stage as the strap ons ignite - the south and light would be amazing.

We NEED to get 4K launch pad and onboard camera footage from ISRO and these be released for soothing IMAX and 4K films to natgeo/disc/cinema halls ....... cmon isro, dharma alone does not win the war.

[SSridhar]

The firing will be repeatedly at the perigee to increase the apogee increasingly.

[sooraj]

Chandrayaan-2 by SEEKER

[Mort Walker]

At 3AM IST in Chennai, there is significant 94% cloud cover and a 36% chance of precipitation with 83% humidity. INSAT images from 14 July at 19:00 IST are showing significant cloud build up to the west and there could be a thunderstorm at the time of launch. I do not wish for the GSLV MkIII-M1 to be hit by lightning. I know there is sufficient shielding and grounding to the chassis where it shouldn't make a difference.

After about 17 minutes from launch, Chandrayaan-2 should separate and begin its earth orbit. To about 3:08AM IST, I will be holding my breath.

[krishGo]

At 3AM IST in Chennai, there is significant 94% cloud cover and a 36% chance of precipitation with 83% humidity. INSAT images from 14 July at 19:00 IST are showing significant cloud build up to the west and there could be a thunderstorm at the time of launch. I do not wish for the GSLV MkIII-M1 to be hit by lightning. I know there is sufficient shielding and grounding to the chassis where it shouldn't make a difference.

After about 17 minutes from launch, Chandrayaan-2 should separate and begin its earth orbit. To about 3:08AM IST, I will be holding my breath.

Launch will be scrubbed if there is significant lighting risk. Rain itself is fine. If there are heavy thunderstorms accompanied by lightning in the area, the launch will postponed. And on the launchpad itself the vehicle is well protected from lightning strikes. The 4 high towers we see around the launchpad are specifically built for this reason.

[Kakarat]

Presently there is no lightning around SHAR

[prasannasimha]

Why are they launching at night? Got delayed to monsoon season so can’t really help overcast weather....

It is because of the argument of perigee and the timing needed to have appropriate translunar injection so there are every day certain launch windows and this has to correspond to land on day1 of the 15 earth days of the lunar day

[prasannasimha]

so instead of circularing a highly elliptic launch orbit (for regular GSO sats) this time it will make the ellipse major axis longer & longer and then finally escape into the lunar transfer path. then reverse on other side to make ellipse into a circle before lander detaches.

it will be a real coup, and a 'chetawani' if we can do this nose to tail.

I wish I could be a fly on the wall right next to the 1st stage as the strap ons ignite - the south and light would be amazing.

We NEED to get 4K launch pad and onboard camera footage from ISRO and these be released for soothing IMAX and 4K films to natgeo/disc/cinema halls ....... cmon isro, dharma alone does not win the war.

This was what they did for Chandrayaan 1 and MOM too

[prasannasimha]

[prasannasimha]

[prasannasimha]

The videos have become pretty slick. If you see the landing site video with full music and full screen it looks really good. short and striking.

[prasannasimha]

The videos have become pretty slick. If you see the landing site video with full music and full screen it looks really good. short and striking.

[Amber G.]

Why are they launching at night? Got delayed to monsoon season so can’t really help overcast weather....

If only it was that easy.... ..

Hope people don't mind stating some obvious things and some physics .. But these things need a very precise "mooharat". The starting point (Sriharikota) is fixed. The end point is fixed (except for a few hundred meters to be chosen later). The time to land is also fixed (beginning of the solar day on moon so that you have full day -14 earth days for solar panels to work) . It may seem there are choices later to adjust but to
arrive at the fixed landing site with the right time and have right lighting conditions for the descent the journey must be planned to meet constraints this mission planning, primarily in the form of trajectory shaping and the limitation of launch opportunities, known as launch windows.

Here are some general important understandings. (I am just speaking from physics point of view about a few important things - there is much more in actual planning)

Trajectory geometry constraints and spacecraft performance capabilities combined to limit the possibilities.

So let us look closely at the trajectory characteristics. ( An understanding of the interrelation of operational constraints and trajectory shaping is essential to understand to give some idea how much work has gone through by our scientists). Let us take each phase:

Launch phase:
Daily window which had a duration of a few hours during a given 24 hour period.
Monthly window which consisted of a few days during a given month or lunar cycle.

- Factors are Range Safety (Direction chosen from the launch sites is limited and thus the time window)
-Booster Performance- (One wastes too much fuel if the optimum time is delayed)
- Insertion Tracking- - ( operational requirement to track the space vehicle for at least 3 minutes after earth orbit insertion in order to make a GO / NO-GO for orbit decision - this should be reachable from the tracking station)

There are similar restraints for
- Earth parking orbit phase

- Trans lunar injection

- Trans lunar coast phase

- Lunar orbit phase
ityadi ityadi ..so each thing has to be planned in advance very carefully..
Hope this helps.

[Mort Walker]

I believe ISRO has set a +/- 10 min launch window. The 20-hour countdown commenced taking weather forecast into effect.

[SwamyG]

Amber, thanks for fascinatingly describing the various factors. For no reason they call it "rocket science"

Whatever happens, I am in a celebratory mood. Just to have this vision and go for this is goosebumps moment.

[SwamyG]

Here is DD youtube streaming....3 more hours to go: https://www.youtube.com/watch?v=6f_HxuVHfrw

[Amber G.]

Why are they launching at night? Got delayed to monsoon season so can’t really help overcast weather....

It is because of the argument of perigee and the timing needed to have appropriate translunar injection so there are every day certain launch windows and this has to correspond to land on day1 of the 15 earth days of the lunar day

To add/emphasize - As I said in the previous post. Like any this kind of launch - the launch window is likely a few hours only (and for a few days near this date otherwise one has to wait for another month).

[chetak]

maybe there is a certain position of earth and moon they need to align with for most efficient slighshot injection into lunar transfer path.

narrow launch window

[prasannasimha]

This is an old video by NASA that explains it well

[Indranil]

Why are they launching at night? Got delayed to monsoon season so can’t really help overcast weather....

If only it was that easy.... ..

Hope people don't mind stating some obvious things and some physics .. But these things need a very precise "mooharat". The starting point (Sriharikota) is fixed. The end point is fixed (except for a few hundred meters to be chosen later). The time to land is also fixed (beginning of the solar day on moon so that you have full day -14 earth days for solar panels to work) . It may seem there are choices later to adjust but to
arrive at the fixed landing site with the right time and have right lighting conditions for the descent the journey must be planned to meet constraints this mission planning, primarily in the form of trajectory shaping and the limitation of launch opportunities, known as launch windows.

Here are some general important understandings. (I am just speaking from physics point of view about a few important things - there is much more in actual planning)

Trajectory geometry constraints and spacecraft performance capabilities combined to limit the possibilities.

So let us look closely at the trajectory characteristics. ( An understanding of the interrelation of operational constraints and trajectory shaping is essential to understand to give some idea how much work has gone through by our scientists). Let us take each phase:

Launch phase:
Daily window which had a duration of a few hours during a given 24 hour period.
Monthly window which consisted of a few days during a given month or lunar cycle.

- Factors are Range Safety (Direction chosen from the launch sites is limited and thus the time window)
-Booster Performance- (One wastes too much fuel if the optimum time is delayed)
- Insertion Tracking- - ( operational requirement to track the space vehicle for at least 3 minutes after earth orbit insertion in order to make a GO / NO-GO for orbit decision - this should be reachable from the tracking station)

There are similar restraints for
- Earth parking orbit phase

- Trans lunar injection

- Trans lunar coast phase

- Lunar orbit phase
ityadi ityadi ..so each thing has to be planned in advance very carefully..
Hope this helps.

I was about to write something similar. The target point in space and time is fixed. The path to that point is fixed, the speeds along that point is fixed, so launch time is also pretty "fixed".

But then I held back because I am pretty sure that ISRO (and any other space agency) has planned for contingencies. For example, one of the orbit raising maneuvers on MoM did not work perfectly and they had to adjust. With MoM they had higher flexibility because they had to synchronize only with Mars orbit around the sun and not its night and day. I do not know how much flexibility ISRO has with Chandrayaan 2. I mean if one of the earth bound or moon bound orbit adjusting maneuvers goes wrong, will ISRO still land on the same lunar day (sacrificing daytime spent on moon) or will it wait for the next dawn?

[Mort Walker]

ISRO set a launch window of 9-16 July. If for a minor reason like weather, a delay, then they can still launch in the next day or so. If there is a technical problem, then another date will have to selected.

It’s more important to get this right rather than rushing.

[Indranil]

That's what I was thinking. They will have extra orbit cycles to account for contingencies.

[Amber G.]

This is an old video by NASA that explains it well

>>YouTube >>> G8xkYel9p-0

This is really very good. Scientifically accurate, yet explains it well. Thanks for posting it.

****
For fun I tried to calculate (the old-fashioned way using basic physics) the possible launch windows.. if we want to land where we plan to land (near south-pole (prime site) 70.90267°S 22.78110°E and (Alternate) -67.87406°S 18.46947°W) in the beginning of local morning (so that there is whole 14 days (lunar day) sunlight and launch from Satish Dhawan Space Centre in a day time.. I don't think we have any launch window in 2019 for daytime launch.. (or 2020).. (possible launch windows (just for making sure we reach moon's orbit wit reasonable inclination) are quite few even for night-time)

Now I am not using computer/orbit_calculatting_software so it is possible that I may be missing some thing.. but I don't think there can be a day time launch. for Chandrayaan II.

[NRao]

Live telecasts:

PIB

Launch of GSLV MkIII - M1 / Chandrayaan - 2 Mission – LIVE from Satish Dhawan Space Centre

Watch Live Launch of GSLV MkIII-M1/Chandrayaan2 on July 15, 2019 from 02:30 hrs IST onwards

[krishGo]

ISRO set a launch window of 9-16 July. If for a minor reason like weather, a delay, then they can still launch in the next day or so. If there is a technical problem, then another date will have to selected.

It’s more important to get this right rather than rushing.

It is also interesting as to what happens when launches are scrubbed.

If the launch is moved to the next day, the propellants on the cryogenic stage and the hyperbolic core stage have to be emptied. They will need to be refueled again before launch. The vehicle stays on the launch pad.

If the launch is postponed to a much later date (say a week or so), the propellants will be emptied and the vehicle will be moved back into the Vehicle Assembly building. They payload with its shroud will also be seperated and then reassembled closer to launch.

[SwamyG]

Filling of Liquid oxygen in cryogenic stage of #GSLVMkIII-M1 completed and filling of Liquid Hydrogen is in progress.
#Chandrayaan2 #ISRO
Updates to continue..

[Amber G.]

<snip> ..
I was about to write something similar. The target point in space and time is fixed. The path to that point is fixed, the speeds along that point is fixed, so launch time is also pretty "fixed".

But then I held back because I am pretty sure that ISRO (and any other space agency) has planned for contingencies. For example, one of the orbit raising maneuvers on MoM did not work perfectly and they had to adjust. With MoM they had higher flexibility because they had to synchronize only with Mars orbit around the sun and not its night and day. I do not know how much flexibility ISRO has with Chandrayaan 2. I mean if one of the earth bound or moon bound orbit adjusting maneuvers goes wrong, will ISRO still land on the same lunar day (sacrificing daytime spent on moon) or will it wait for the next dawn?

To be clear, there is *some* flexibility in the sense that one can wait for a orbit or two (measured in hours) and return to the same point to fire rockets for trans-lunar orbit. Same thing when Vikram separates from the orbiter - which it will do after mapping the area and choosing the site. But flexibility is not too much - can wait for a few orbits around moon but window is still within a day or so , otherwise the light conditions to land on moon will change and you do want to land as close to lunar - morning so that Pragyan has sunlight for 14 days of power.

But orbit(s) (both parking orbit around earth and final parking orbit around moon) have to have correct inclination and position of the perigee. To be clear, here our reference system fixed to the stars and not the "spinning" earth. IOW the position of Satish Dhawan Space Centre is changing wrt to time.. that's why the launch window is time-sensitive.
Similarly if there is tracking etc.. the time factor enters because you want it to be right time that tracking system is below the orbit at the right time...

Hope this helps. (More accurate explanation of the launch window may be that Satish Dhawan Space Centre is at the "right position" around 2AM )