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.
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.
Gagan wrote:Night launch !!!
So the visuals will be short
Is it overcast or clear skies over Sriharikota or chennai?
Mort Walker wrote: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.
Katare wrote:Why are they launching at night? Got delayed to monsoon season so can’t really help overcast weather....
Singha wrote: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.
Katare wrote:Why are they launching at night? Got delayed to monsoon season so can’t really help overcast weather....
prasannasimha wrote:Katare wrote: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
Singha wrote:maybe there is a certain position of earth and moon they need to align with for most efficient slighshot injection into lunar transfer path.
Amber G. wrote:Katare wrote: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.
prasannasimha wrote:This is an old video by NASA that explains it well
>>YouTube >>> G8xkYel9p-0
Mort Walker wrote: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 wrote: <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?
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