Chandrayaan-II, All Chandrayaan-II related articles Options

[Thorsten Denk]

Chandrayaan-2 launch now NET May.

https://www.asianage.com/science/010419/isr...ay-k-sivan.html

Thorsten

[Phil Stooke]

Another month, another date: mid-July.

https://twitter.com/isro/status/1123612384336027650

And that tweet has a name for the rover, Pragyan, meaning Wisdom according to Wikipedia, or Knowledge according to New Delhi TV.

Phil

[John Moore]

India's Chandrayaan 2 lunar mission to the Moon has successfully launched today, 22 July 2019 (at 0913 GMT) from its space centre in Sriharikota, near the Bay of Bengal.

Already having separated from its launcher's second stage and now in Earth orbit, Chandrayaan 2 is expected to touchdown on the lunar South Pole some time in early September 2019.

The mission includes both a lander and rover (also with an orbiter overhead); where all three include various research instruments (13 of Indian, 1 of NASA) used in areas, for example:
looking for water and minerals signatures, and the study of moonquakes and possible future landing sites...amongst other activities. The orbiter has eight instruments, the lander with
four (including the NASA instrument), while the rover has the remaining two.

On touchdown, the solar-powered rover will off-load from the lander after some four hours, where it will then mainly rove around the surface during lunar day-long (14 earth days) stints.

[Thorsten Denk]

Finally they're on their way.

Lunar Landing is expected Sept 7 at 2:50 AM Indian Standard Time or Sept 6 at 21:20 UT.
Friday evening for Europe, afternoon for America.

... Chandrayaan 2 is expected to touchdown on the lunar South Pole some time in early September 2019.

I wonder why all the time they say "on the South Pole".
The landing Site is at 70°S, this is still 600km from the pole.
It's the nearest lunar soft landing to a pole ever, but not yet "on" the pole...

Thorsten

[Phil Stooke]

Here is a set of 'finder' maps for the primary landing site and the alternative site.

Phil

[John Moore]

Just querying: while during the long, lunar day (14 earth days) stints that the Chandrayaan 2 rover (Pragyan) is expected to undergo near/below the 70.0s degree South Pole environment, will
the different, southerly periodic lighting conditions, let alone the temperatures changes, affect the amount of days that the rover can rove (I'm thinking that the various powering down/up
periods might be shorter: simply due to less illumination time on the solar panels at such latitudes, but then, do the lower temperature differences, lighting conditions counteract such - allow longer exploration times).

John

[MahFL]

Gratz to ISRO on a successful launch.

[Explorer1]

Perhaps the 'noon naps' that Yutu has been commanded to do to avoid overheating might not be necessary, if the sun never gets too high above the horizon?

I'm certainly looking forward to surface images, both in terms of long shadows and Earth near the horizon....

[JRehling]

The amount of solar radiation that the panels receive will depend upon the angle between the panels and the Sun. The angle of the ground to the Sun is irrelevant. The imagery I see online indicates that the solar panels are not horizontal, so I presume that they will be oriented for better energy production.

[Thorsten Denk]

Hi all!

Some thoughts:

"Noon naps" (here in Spain: siesta) are probably not necesary, because the sun never rises more than 20deg above the horizon. This keeps the surface temperature rather low.
Thermodynamic equilibrium:
- Max. solar irradiation on horizontal surface: 1367W/m² x cos(70°) = 470W/m²
- Thermal reradiation: 470 = 5.67e-8 x T^4
=> Noon-Temperature T = 301K = 28°C (like here last night )
This is approximately, no reflection of sunlight or emittance of IR <1 was included.
But in any case, not as hot as on other places.

At the time of landing, the terminator is at 0deg longitude. The landing site is at 23°E, this means that at this site, the sun is already 1.5 Earth-days up. This has to be taken into account when somebody speaks about "14-Earth days operation time". It will be not more than 12.5 Earth days. If they achieve night survival, then it will be more of course. (This does not take into account possible "seasonal effects". As the Moon's axis is tilt only 1.5° vs the ecliptic, this is normally negligible, but not when coming close to a pole. 70°S is not yet close enough to be important, but I wouldn't be surprised if they could win (or loose) another half a Earth-day or so. And, of course!, terrain also matters! If there's a small hill in the west, the sunset might be significantly earlier.)
If somebody wants to do detailed calculations, this great page helps: https://trek.nasa.gov/moon/index.html

The solar panels of the lander and the rover are mostly vertical. As far as I can see on the photos, neither panel is steerable.
The lander has one side (I suppose this will face south) with the rover and without solar panels, another two sides (I suppose facing east and west) with solar panels, and one side (I suppose facing north) that's never visible in the photos, so I don't know what's there. Hopefully another solar panel. If not, they will have a hard time around local noon.
The lander has one solar panel that can be flipped to vertical, but doesn't seem to be steerable! This means that the lander should always move or at least park in a sun facing direction! Remember, over the lunar day, the sun will move in the sky from east (at the horizon) to north (elevation <20°) to west (again at the horizon).

I wonder how they will manage the landing on a safe spot. The sun is very low during landing, and the shadows will be very long. A system like the one used by Cháng'é-3 and 4 (imaging, terrain recognition) will probably have a hard time to work.

Shadows, yes, it will be interesting to see how they will hamper (or not?) the navigation of the rover.

Somebody knows what capabilities they have to detect water?
I don't expect it directly on the surface, but not too many cm below, there might be traces.

Now let's cross fingers that they are successful with the flight and the landing. This place will give a first small hint about how the conditions on the real pole might be.

Regards
Thorsten

[John Moore]

While fully admitting to not understanding the temperature/power complexities of sunlight falling on the lander and rover solar panels at such extreme latitudes, your description, Thorsten, is wonderful. Thanks

John

[elakdawalla]

Note that the lander and rover are not expected to survive the lunar night. Their mission will last one lunar daytime, 14 Earth days, according to mission materials. I'm a little confused by this number because I can't imagine a successful landing during the very twilit high-southern-latitude dawn; it seems to me they'll have to land under relatively high sun conditions. But that's speculation on my part.

[Phil Stooke]

The statement is ambiguously worded, but I think they are saying 'the lander and rover will last for one lunar day' and 'one lunar day is 14 Earth days'. I saw it said somewhere that the landing is about 36 hours after sunrise, so you are quite right that the actual surface missions must be shorter. We can probably expect a maximum of 12 days operation. We had better hope a noon siesta is not required!

Phil

[elakdawalla]

Thanks, I had missed that detail. I'm still impressed by a landing 36 hours after sunrise at that latitude!

[nogal]

The Chadrayaan-2 mission seems to be proceeding according to plan, the probe having successfully completed all the Earth orbit raising manoeuvres on August 6. The next orbital change is the trans-lunar injection, scheduled for August 14.
Here is a comparison table for the attained and planed orbits.


The information is taken from the Updates web site and the mission plan
Fernando