Author Topic: Chandrayaan-2 Mission - Launch and Landing Coverage  (Read 479679 times)

Offline seshagirib

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #740 on: 08/02/2019 10:46 am »
"Hi resolution mapping of the landing area by the orbiter, uploading the terrain maps to the lander, and fine tuning of the exact landing spot will need to be  done in a shorter time - but still about ~15 days must be more than ample."

We know that the lander will spend less time in orbit because of the launch delay.  But 15 days will not be ample for mapping the landing site because the site will be in darkness most of that time.  The landing is shortly after sunrise (36 hours after sunrise, I believe), so it will be in darkness for 14 out of the 15 days.

Not to worry, because ISRO has access to all the LRO images in PDS, including stereo images, and it can do all the mapping it needs without using its own high resolution camera (and that has already been done and reported at LPSC this year, albeit in a print-only abstract).  The camera on Chandrayaan 2's orbiter will be most useful for post-landing documentation.

As mentioned by vikranth, ISRO says the lander(vikram) will be updated with the high resolution images of the landing site captured by the orbiter.
Maybe the lander (optimally?) needs the images of the  landing site at sunrise - brightness, shadows, crater illumination etc.  These images at dawn may or may not be readily available in library images ( LRO or others).  -All this is just my guess.

Offline Olaf

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #741 on: 08/02/2019 11:10 am »
https://www.isro.gov.in/update/02-aug-2019/chandrayaan2-update-fourth-earth-bound-maneuver
Quote
Chandrayaan2 update: Fourth earth bound maneuver
Fourth earth bound orbit raising maneuver for Chandryaan-2 spacecraft has been performed successfully today (August 2, 2019) at 1527 hrs (IST) as planned, using the onboard propulsion system for a firing duration of 646 seconds. The orbit achieved is 277 x 89472 km.
All spacecraft parameters are normal.
The next orbit raising maneuver is scheduled on August 6, 2019, between 1430 – 1530 hrs (IST).

Offline seshagirib

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #742 on: 08/02/2019 11:17 am »
https://www.isro.gov.in/update/02-aug-2019/chandrayaan2-update-fourth-earth-bound-maneuver
Quote
Chandrayaan2 update: Fourth earth bound maneuver
Fourth earth bound orbit raising maneuver for Chandryaan-2 spacecraft has been performed successfully today (August 2, 2019) at 1527 hrs (IST) as planned, using the onboard propulsion system for a firing duration of 646 seconds. The orbit achieved is 277 x 89472 km.
All spacecraft parameters are normal.
The next orbit raising maneuver is scheduled on August 6, 2019, between 1430 – 1530 hrs (IST).

A small short fall, orbit planned: 248 x 90229 km. - may be they will catch up in the next burn , or TLI, or mid course corrections ( if any ).

Offline Phil Stooke

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #743 on: 08/02/2019 07:17 pm »
Good points, all, and thanks for this.  The only opportunity to do this will be on the orbit before the descent (or possibly the orbit before that, or during the descent) - otherwise, either the site is in darkness or the orbiter is not over the site as it crosses that latitude.  You are right that an image with lighting matching the actual descent conditions would be best for an image matching algorithm, if that is used to guide the lander to a particular spot. 

We also know that hazard avoidance will be used by the lander during descent.  Twice it will hover briefly (at 400 m and 100 m, I think) while onboard image processing looks for a safe spot to land.  Chang'e 3 and 4 also did this, but no previous robotic landers attempted it.

My guess, putting this together, is that potential sites in the landing ellipse will be chosen ahead of the landing based on LRO images.  Images taken from orbit during the descent orbit or the one before will be fed to the lander computer for image matching purposes to guide the lander to the desired spot.  Finally, hazard avoidance imaging by the lander will refine the exact landing point.

Best wishes to Vikram and Pragyan!


Offline Olaf

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Offline tappa

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #745 on: 08/06/2019 11:50 am »
Chandrayaan2 update: Fifth earth bound maneuver

Quote
Fifth earth bound orbit raising maneuver for Chandryaan-2 spacecraft has been performed successfully today (August 6, 2019) at 1504 hrs (IST) as planned, using the onboard propulsion system for a firing duration of 1041 seconds. The orbit achieved is 276 x 142975 km.

All spacecraft parameters are normal.

The next maneuver is Trans Lunar Insertion (TLI), which is scheduled on August 14, 2019, between 0300 – 0400 hrs (IST).

Offline sanjaykumar

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« Last Edit: 08/08/2019 02:54 am by sanjaykumar »

Offline seshagirib

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #747 on: 08/11/2019 06:49 am »
Hoping for and looking forward to, broadcast ( at least a webcast) for important upcoming events like TLI, LOI, and the Landing.

Offline Steven Pietrobon

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #748 on: 08/11/2019 08:45 am »
I don't expect a webcast for TLI and LOI since there won't be anything to see (other than telemetry data), but hopefully there will be a webcast for the landing, where pictures or video of the landing might be transmitted.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline input~2

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #749 on: 08/11/2019 09:29 am »
 
Quote from:  Intelsat's FCC filing
Intelsat requests an expedited grant of Special Temporary Authority for three days, commencing August 13, 2019, to utilize a 7.3m S-band antenna located at its Paumalu, Hawaii teleport to receive telemetry signals from the Chandrayaan-2 spacecraft as it transits to the Moon. Chandrayaan-2 launched on July 22, 2019. Intelsat is seeking expedited treatment because, due to unforeseen circumstances, the original antennas that were planned to support the spacecraft’s maneuvers on August 13th will not have coverage of the spacecraft when the maneuvers will occur. Intelsat expects to receive telemetry for approximately five minutes on August 13, 2019.

Offline seshagirib

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #750 on: 08/11/2019 12:12 pm »
I don't expect a webcast for TLI and LOI since there won't be anything to see (other than telemetry data), but hopefully there will be a webcast for the landing, where pictures or video of the landing might be transmitted.

Just as they did for Mangalyan's MOI.

They can spice this up with spacecraft animation:
-orienting of the space craft before the TLI and LOI burns.
-animation of the engines and attitude thrusters firing.
-maybe even a good bye image of the earth-TLI, and a welcome image of the moon-LOI.

This will hopefully keep the general populace ( particularly in India ) involved and enthused

Offline Astro_Neel

Has anyone looked into the locations of payloads and tried to figure out where exactly have they placed NASA's retroreflector on it? I've looked into all kinds of resources to get a glimpse of it, but couldn't find it anywhere. This is the only one I'm having trouble finding despite knowing the fact that it should be someplace on top of the lander facing upwards to be in line of sight with the incoming laser.

For every other payload, we know the location already (with very little changes), thanks to this image. Let me know if you have any clues about where that LRA is.
Per Aspera Ad Astra ✨

Offline seshagirib

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #752 on: 08/12/2019 05:29 am »
Also, cannot find any description / location of the surface camera(s) on the lander(surely there must be at least one). The rover seems to have one front facing camera.

Offline Steven Pietrobon

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #753 on: 08/12/2019 06:44 am »
The reflector is pretty small. You might want to ask ISRO where the reflector is.

https://www.space.com/next-gen-apollo-moon-laser-reflector-on-india-mission.html
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline ddspaceman

Chandrayaan 2 To Leave Earth’s Orbit Tomorrow To Reach Moon As Per Schedule On 20 August; Landing On 7 September

https://swarajyamag.com/insta/chandrayaan-2-to-leave-earths-orbit-tomorrow-to-reach-moon-as-per-schedule-on-20-august-landing-on-7-september


« Last Edit: 08/13/2019 12:42 pm by ddspaceman »

Offline lamid

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #755 on: 08/13/2019 08:12 pm »
TRAJECTORY Chandrayaan-2:
  This is a merge of post-launch trajectory solutions fit to tracking data
  through 2019-Aug-12, with a prediction extending to Aug 15.
Trajectory name                             Start (TDB)        Stop (TDB)
  ch2o_spk_190722-[190810_od0*]_v*_dsn.V0.* 2019-Jul-22 09:31 2019-Aug-15 12:00

https://ssd.jpl.nasa.gov/horizons.cgi#results


Offline Steven Pietrobon

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #757 on: 08/14/2019 05:28 am »
Looks like ISRO has a nice animation of TLI.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline lamid

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #758 on: 08/14/2019 05:44 am »
TRAJECTORY:
  This is a merge of post-launch trajectory solutions fit to tracking data
  through 2019-Aug-12, with a prediction extending to Aug 21.

  Trajectory name                             Start (TDB)        Stop (TDB)
  ch2o_spk_190722-[190810_od0*]_v*_dsn.V0.* 2019-Jul-22 09:31 2019-Aug-21 03:45


From data
335 x 405 115 km

Offline s^3

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Re: Chandrayaan-2 - GSLV MkIII - July 22, 2019 (09:13 UTC)
« Reply #759 on: 08/14/2019 05:38 pm »
3D representation of the Orbit Geometry post TLI manuever.

First a general view of a combination of Earth, Moon and CH2 orbits(after 5th ORM ) depicting
1. What would have been the undisturbed orbit if TLI was not done
2. Post TLI new orbit carrying CH2 from Earth's Gravity to Lunar gravity
3. Propose LOI 1st burn tossing the CH2 in 18000 kms orbit around Moon.

The Blue triangle is the Neutral Point where both Earth's gravity and Moon's gravity are equal andthe s/c enters Lunar gravity field.
This transition happens in the early hours of 17th August.


 

2nd image shows the same situation in ( nearly ) in-plane orbit of the CH2 orbit.

Notice how the craft nears moon and how the orbit inclination changes to nearly North-South after 1st LOI. 1st LOI sends the CH2 in 118km x18078km orbit around Moon.


« Last Edit: 08/15/2019 03:06 am by s^3 »

 

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