Aditya-L1 (आदित्य -L1): Launch and Discussions

[Amber G.]

Just for perspective:

Sun-Earth distance is 151 million km.
Earth-L1 distance is 1.5 million km. 1% of the former.

Earth Moon distance is 0.384 million km. One fourth of earth-L1 distance.

Don't popular infographics mislead you. Get the right spatial perspectives.

[Amber G.]

It seems L1 is unstable, which means any perturbation from the exact L1 point results in a (fictitious) force which tends to accelerate the object away from the point. This seems like the opposite of being in orbit around an attractor - it's like being in orbit against a repeller (if you know what I mean). The other difference from being in orbit around a gravitational well seems to be that with a gravitational well, the attractive force increases as one gets closer. Whereas with the L1 point, the "repulsive force" would increase with distance. Is this the reason why the orbital dynamics around the L1 point are so complex?

L1 is unstable equilibrium. But analogy of opposite of "gravitational well" is not entirely accurate. "repulsive force" as you put is not uniform with respect to direction. A better analogy, instead of "well" it is a "saddle point" .. it depends on which direction (in three dimensional space) you go..

L1 saddle point


The orbits (using minimum fuel) are quite complex - Halo are periodic orbits -- there are Lissajous orbit too (Electrical Engineers / physicists may remember Lissajous figures on oscilloscopes) -- which are not periodic..

[sudarshan]

Thanks, I got the saddle point analogy. So moving away in certain directions results in a restoring force, but in other directions, it tends to pull the object away.

Orbiting a gravitational well like the earth or the moon, I guess one can just keep track of altitude from the surface (or center) of the object and make corrections (of course, there could be other attractors to keep track of). But around the L1, it seems it would be necessary to keep track of both the 3-d vector position, and the 3-d vector velocity, and then make on-the-fly calculations as to the vectored thrust necessary to maintain orbit. Sounds fascinating. Would this be a chaotic phenomenon?

[sanman]

L1 is unstable equilibrium. But analogy of opposite of "gravitational well" is not entirely accurate. "repulsive force" as you put is not uniform with respect to direction. A better analogy, instead of "well" it is a "saddle point" .. it depends on which direction (in three dimensional space) you go..

L1 saddle point

Hey, thanks for that nice illustration. So this amounts to a "partial well" or "uni-axial well" in a sense that moving along particular axis tends to restore back to equilibrium, while moving in another (orthogonal) direction seems to result in falling out of balance?
I can understand the "falling out" part more easily: ie. if I'm trapped between 2 opposing influences, then moving toward one and away from the other will put me out of balance.
But the restoring force that occurs when shifting along the other axis is not so clear to me - why does that part happen again? What's physically going on there?

[bala]

Meet Dr. Nigar Shaji from Tenkasi in Tamilnadu. She is ISRO's Aditya-L1 mission project director. She is a muslim. Amazing individual whose dedication to the project comes through and through in the interview. Her hardwork, sleepless nights, service to the nation must make all Indians very proud.



// tis the power of India wherein a scientist can be women, muslim and shine in a premier scientific endeavor. So many vitriolic lectures by the West on faltu nonsensical accusations on India!

[SSridhar]

Aditya-L1 healthy, first Earth-bound manoeuvre puts spacecraft in 245km x 22,459km orbit

Isro scientists on Sunday successfully completed the first Earth-bound manoeuvre of Aditya-L1, India’s first solar space observatory mission that was launched on Saturday (September 2).

“The satellite is healthy and operating nominally. The first Earth-bound manoeuvre (EBN1) was performed successfully from Istrac (Isro Telemetry Tracking and Command Network) in Bengaluru. The new orbit attained is 245km x 22459 km,” Isro said, adding that the second Earth-bound manoeuvre is scheduled for 3am on September 5.

Sunday marked the first of the 16 days Aditya-L1 will stay in Earth-bound orbits and EBN1 was the first of the five manoeuvres around Earth, during which the spacecraft will gain the necessary velocity for its journey.

Subsequently, Aditya-L1 will undergo a Trans-Lagrangian1 Insertion (TLI) manoeuvre, marking the beginning of its 110-day trajectory to the destination around L1. Upon arrival at the L1 point, another manoeuvre binds Aditya-L1 to an orbit around L1, a balanced gravitational location between the Earth and the Sun.

The TTC group has been having a hectic time recently. Well done.

[juvva]

Thanks, I got the saddle point analogy. So moving away in certain directions results in a restoring force, but in other directions, it tends to pull the object away.

Orbiting a gravitational well like the earth or the moon, I guess one can just keep track of altitude from the surface (or center) of the object and make corrections (of course, there could be other attractors to keep track of). But around the L1, it seems it would be necessary to keep track of both the 3-d vector position, and the 3-d vector velocity, and then make on-the-fly calculations as to the vectored thrust necessary to maintain orbit. Sounds fascinating. Would this be a chaotic phenomenon?

i am reasoning like this:
let the z axis be the line connecting sun and earth.
and the x-y plane be the plane orthogonal to the z-axis.

now if the s/c at L1 is moved in the x-y plane, the combined gravitational pull of earth and sun should pull it back towards L1 point.( the vector sum would cancel out in the z-direction , and the vector sum in the x-y plane would be in restorative direction)

but if the s/c should is moved in the z direction, it would start falling towards the sun, or earth depending on which direction it is disturbed. The s/c will have to use its thrusters to move back to L1.

i am sure this is a oversimplification but may be a starting point ...

[sanman]

[Amber G.]

#AdityaL1 is tracking as predicted to http://Space-track.org TLEs

[SSSalvi]

Thanks, I got the saddle point analogy. .........

i am reasoning like this:
let the z axis be the line connecting sun and earth..........

Using

My simplistic view to look at it is like this:

The Left Portion of Halo orbit is a part of the Earth orbit with Apogee slightly >L1 distance so slightly faster than L1 velocity wrt Earth
The Right portion of Halo orbit is akin to a Sun orbiting planet with slightly < Earth-Sun distance to faster than Earth.
Both Sun and Earth are playing Ping-Pong with A-L1 Ball.

Just a Logical view without Maths rigours.

[SSridhar]

In a first, Isro uses high throughput X-band frequency for Aditya mission - ToI

Isro has achieved a new milestone, graduating from the S-band telemetry and command regime used for communication with its space modules to a high throughput X-band frequency for Aditya-L1, India's first solar space observatory that completed the first of five Earth-bound manoeuvres at 11.40am Sunday.

So far, Isro had used X-band only for payload data downloads.

Compared to S-band, which operates with 2-2.5GHz, X band functions with 8-8.5GHz. This is in line with global standards for missions beyond Earth's sphere of influence.

The major advantage of using X-band is that it allows for more clear communication with distant satellites. In the case of Aditya-L1, the distance is 1.5 million km.

After Aditya-L1 completed the first Earth-bound manoeuvre, Isro said, "The satellite is healthy and operating nominally. The new orbit attained is 245km x 22,459km and the second Earth-bound manoeuvre is scheduled for 3am on September 5."

Aditya's operations are being carried out by multiple tracking stations operated by the Isro Telemetry, Tracking and Command Network (Istrac), headquartered in Bengaluru. The set-up includes a temporary station in the Fiji Islands, about which TOI was the first to report in January.

The main antenna supporting operations is an 18m one in Byalalu, some 30km from Bengaluru. Commissioned in 2021, the antenna was set up using funds for the Aditya-L1 mission, which was designed to have X-band telemetry.

It is equipped with auto-tracking features across both bands and remotely operable from the network control centre.

"We have used this even with Chandrayaan-3. The antenna at Byalalu, developed by ECIL (Electronics Corporation of India Limited) with some key systems coming from BARC (Bhabha Atomic Research Centre), can operate in both S and X bands," Isro chairman S Somanath told TOI.

Isro has adopted the strategy of building stations that can use both bands as other missions - like remote sensing, communication satellite and commercial launches - use S band.

Apart from the Byalalu antenna, Isro has at least two smaller antennas that can operate in both S and X bands.

The new infrastructure will also provide opportunities for space PSU NewSpace India Limited (NSIL) to commercialise it.

I am happy TTC operations are also getting highlighted because otherwise they are the usual silent and unforeseen brains behind.

[SSridhar]

The Halo Orbit is quasi-periodic but still needs station-keeping (i.e. engine burns to keep Aditya in correct orbit). We had a very precise lunar injection which preserved a lot of fuel, in the case of CY-3. We must hope that our SOI and the S-E L1 insertion are so precise that the life of Aditya would be more than what is planned for. Usually, our spacecraft insertions into orbits have been extremely precise leading to longer life.

[Amber G.]

....
My simplistic view to look at it is like this:

The Left Portion of Halo orbit is a part of the Earth orbit with Apogee slightly >L1 distance so slightly faster than L1 velocity wrt Earth
The Right portion of Halo orbit is akin to a Sun orbiting planet with slightly < Earth-Sun distance to faster than Earth.
Both Sun and Earth are playing Ping-Pong with A-L1 Ball.

Just a Logical view without Maths rigours.

Nice, as usual. Let me add: (Without complex math - but for those who are familiar with ordinary orbits).

Lagrange points like L1 exists for sun-earth type systems, where larger body (sun) is at least about 25 times more massive than smaller body ( Earth). This mass ratio is true for Earth-Moon system too.

For simplicity let us assume circular orbits.. around sun. (Actual orbit of earth is ellipse, which makes math a little complex )

Let us just consider sun (as it is massive). Earth which is about 150,000,000 Km away goest around it in 1 year. so do other planets.



At L1 - If we neglect the effect of the earth - a sat will go faster around sun, completing the orbit in less than an year (like Venus etc).

The effect as seen from earth .. Sat will go 'ahead' of sun in a short time..and keep increasing this angular distance)

But Earth is there. It is smaller than sun but L1 is closer to it so it does have influence... it slows L1 -- sorts of drags it with it..
This slowing down is just right enough to keep the sat at the same position (with respect to sun - as seen from earth)..always on the line joining earth/sun.

We call L1, unstable equilibrium. A slight perturbation - 'drag' from earth will not cancel out the difference in centrifugal forces -- and in some time sat will be nothing but another object in an (elliptical) orbit around sun. Nothing stationary now..

These perturbations are there - due to Jupiter, Venus etc which have their own influences.

A sat in the vicinity of L1 goes through complex orbit -- which , if you look from earth resembles a "halo" or a ring. These are complex orbits (in three dimensions).. some are periodic (Halo) and some are not (Lissajous orbits) but they are bounded.

Some periodic "station keeping" is needed to keep these orbits in check -- The fuel requirement is quite low ( My back of envelop calculations -- delta_V about 0.5 m/s ).. but key point here is 'right thrust' at exactly the right time.. So if you have an excellent navigational system, and control system, you can stay for decades with small amount of fuel.

----
Most popular articles do not do justice to describe these orbits properly. For example the size of the orbits is of the order of distance of moon from earth...

Here is a figure, I like to use - to represent the orbit in better perspective -- (Taken from SOHO's orbits)

[sudarshan]

So theoretically it is possible for Venus to be pulled into the L1 point and do a Lissajous dance there for a few hundred thousand years, before going back to a different orbit? Of course, Venus is massive enough, that it will possibly perturb the earth and distort the L1 point's location itself.

But I was thinking about Immanuel Velikovsky and his theories.

[Amber G.]

So theoretically it is possible for Venus to be pulled into the L1 point and do a Lissajous dance there for a few hundred thousand years, before going back to a different orbit? Of course, Venus is massive enough, that it will possibly perturb the earth and distort the L1 point's location itself.

But I was thinking about Immanuel Velikovsky and his theories.

NO.

Immanuel Velikovsky and his theories are beyond absurd. His knowledge of astronomy (and celestial mechanics is much worse than his knowledge of Organic Chemistry where 'Hydro Carbon' (Like petroleum) of the Venus atmosphere becomes 'carbohydrates ' (like sugar) and falls as Manna for Israelites who consumed it for 40 years

(Among other things - Halo orbits are a million km's away (far above earth's atmosphere).. Position of Venus is known to Indians (and others) for thousands of years prior to this so called 'dance'..and if Venus came as close to earth as he describes there would be plenty of evidence.... can one imagine tidal forces alone???

[SSSalvi]

AmberGji,
Any guess of 1 Halo orbit period? Hrs or days?
Played around with SOHO, but could not find any periodicity with different time periods.

[sudarshan]

Immanuel Velikovsky and his theories are beyond absurd. His knowledge of astronomy (and celestial mechanics is much worse than his knowledge of Organic Chemistry where 'Hydro Carbon' (Like petroleum) of the Venus atmosphere becomes 'carbohydrates ' (like sugar) and falls as Manna for Israelites who consumed it for 40 years

Thanks for confirming. I had already discounted most of his theories, when he talked of the "invading Aryans" in 1500 BC in India. However, when I saw the stuff about Lissajous orbits, L1, etc., I started wondering if there could be some theoretical basis behind his theories.

[Amber G.]

AmberGji,
Any guess of 1 Halo orbit period? Hrs or days?
Played around with SOHO, but could not find any periodicity with different time periods.

For SOHO, it is about 179 days... around L1... L1 orbits the sun in 1 year..

Added later; https://solarsystem.nasa.gov/missions/s ... 20months).

[Amber G.]

The second Earth-bound maneuvre (EBN#2) is performed successfully from ISTRAC, Bengaluru. ISTRAC/ISRO's ground stations at Mauritius, Bengaluru and Port Blair tracked the satellite during this operation.
The new orbit attained is 282 km x 40225 km.
The next maneuvre (EBN#3) is scheduled for September 10, 2023, around 02:30 Hrs. IST

[SSSalvi]

Halo orbit of SOHO.

Plotted for 1 year period. Z Axis is highly exaggerated to show the shape.
Sun is at centre ( Green Dot ).
Notice that SOHO ( Yellow Line ) is always within Earth orbit ( Brown ) ... At L1 point traversing North/South.
Will attempt Earth to Sun looking direction later.

[SSSalvi]

Surprisingly, two EBNs over but the latest TLE available pertains to Launch Orbit.

[rrao]

sir jees,
as Aditya goes near to sun , how the inside electronics of Aditya-L1 gets cooled ,because of rising temp and the craft is exposed to sun always.

[Amber G.]

sir jees,
as Aditya goes near to sun , how the inside electronics of Aditya-L1 gets cooled ,because of rising temp and the craft is exposed to sun always.

As said before, Sun - Earth distance is 151 million Km
L1 is 1.5 million Km from Earth (1% of Earth-Sun distance)
The distance from the sun is still 99% ... Aditya is nor really getting 'close' to worry about in this aspect.

[arvin]

^^^
Parker solar probe closest approach to sun will be 6.9 million km in 2025.
They will be able to shield the electronics even at such close proximity.

[bala]

Isn't deep space frigid cold. Sun's heat is when things are captured by an entity and if rays are reflected away, then the apparatus does not heat up.

[Amber G.]

^^^What really matters is that if you put a thermometer at the place you are interested in - what reading it will give...
- Top of Mount Everest in day (when sun is just a little closer at noon) temperature is much lower than say a camp in Thar desert.

JWST telescope, if you put a thermometer near the telescope, it will read about (Minus) - 233 degrees Celsius while expected temperature of Aditya L1 (place where all the electronics will be stored will be about 20-30 degree centigrade..

Note that both JWST (at L2) and Aditya L1 are/would be in deep-space almost the same distance from Sun (151 Km +- 1%).. it all depends on how you shade it from Sun..

[Amber G.]

^^^
Parker solar probe closest approach to sun will be 6.9 million km in 2025.
They will be able to shield the electronics even at such close proximity.

!!!
(To add - at present, the perigee is 8 or 9 million Km from Sun -

[Najunamar]

It is mainly because Aditya’s surface area on which the solar rays are incident is quite small, if the Earth’s orbit itself were to be just this 1% closer we would be toast right?

[Amber G.]

^^^

It is mainly because Aditya’s surface area on which the solar rays are incident is quite small, if the Earth’s orbit itself were to be just this 1% closer we would be toast right?

Short answer NO.
The Earth's climate and temperature are influenced by a complex interplay of factors, and greenhouse gases like carbon dioxide (CO2) have a MUCH more significant effect on Earth's temperature than variations in its orbital distance alone.

(Hint: We had ice ages and warmer periods -- earth orbit did not change much --- Mars, at one time had moderate climate (water etc)..As Carl Sagan once said -- earth can become like our neighbors like Venus or Mars -- with just a slight conditional change in atmospheric gases...

Also just look at Mercury where average temp is 167°C, and Venus where this Average Temp is 464°C) .

(Mercury, despite being the closest planet to the Sun, has a much lower mean surface temperature. During the day, temperatures on Mercury can soar to around 430 degree .. However, because Mercury has a very thin and tenuous atmosphere, it cannot retain heat effectively... at night, temperatures on Mercury plummet to around (Minus) -180 degrees Celsius) (On Venus, night time temperature is not much different than day time temperature)

[Najunamar]

Yes, AmberGji, just 1M miles won't make a difference considering earth does come closer to the Sun every Winter by about 3M miles compared to Summer. But if it geta too close perhaps 10-15 M miles it may trigger a melting of the polar ice caps...

[Piyal.g]

We need to improve our rocket's thrust quickly.
How long will it take for us to reach Venus If we use the slingshot method?
Aditya l1 takes 109 days to cross 1.5 million km, Venus is 61 million km away.
The central government should, first of all, assign funds for NGLV.

[Amber G.]

Yes, AmberGji, just 1M miles won't make a difference considering earth does come closer to the Sun every Winter by about 3M miles compared to Summer. But if it geta too close perhaps 10-15 M miles it may trigger a melting of the polar ice caps...

True... 3M Km closer in early January (Winter in northern hemisphere)..than in early July.

Just some tidbit: Goldilocks zone for Earth -- where earth can sustain life (with approximately present type of atmosphere on earth and our sun) - some say is 0.95 AU to about 1.4 AU

[Amber G.]

We need to improve our rocket's thrust quickly.
How long will it take for us to reach Venus If we use the slingshot method?
Aditya l1 takes 109 days to cross 1.5 million km, Venus is 61 million km away.
The central government should, first of all, assign funds for NGLV.

FWIW: Some comment: Improving rockets is a good thing ... but "Improving rockets" need not help in reaching there "quickly"..
The time it takes for space probes to reach specific destinations can vary widely depending on their launch date, trajectory etc .. propulsion systems may make a difference but only small amount.

Typical time it takes to reach the Sun-Earth L1 point depends on the specific mission and launch date. but typically, it takes several weeks to a few months to reach L1.

The travel time to Venus also varies depending on the launch date and the specific mission goals. On average, it takes about 3 to 6 months to reach Venus when using a direct trajectory from Earth to Venus.

(For missions that use gravity assists or other complex trajectories, travel times may vary --bigger rockets may make orbit calculation easier but do not make a drastic difference ..)

[Piyal.g]

We need to improve our rocket's thrust quickly.
How long will it take for us to reach Venus If we use the slingshot method?
Aditya l1 takes 109 days to cross 1.5 million km, Venus is 61 million km away.
The central government should, first of all, assign funds for NGLV.

FWIW: Some comment: Improving rockets is a good thing ... but "Improving rockets" need not help in reaching there "quickly"..
The time it takes for space probes to reach specific destinations can vary widely depending on their launch date, trajectory etc .. propulsion systems may make a difference but only a small amount.

The typical time it takes to reach the Sun-Earth L1 point depends on the specific mission and launch date. but typically, it takes several weeks to a few months to reach L1.

The travel time to Venus also varies depending on the launch date and the specific mission goals. On average, it takes about 3 to 6 months to reach Venus when using a direct trajectory from Earth to Venus.

(For missions that use gravity assists or other complex trajectories, travel times may vary --bigger rockets may make orbit calculation easier but do not make a drastic difference ..)

If the satellite leaves Earth orbit at a higher speed shouldn't it reach its destination early?
I agree that we have to calculate the optimum path as due to Venus' orbit most of the time the distance between Earth and Venus is higher. But during the launch window also speed will be a crucial factor. Like in case of Maven and MOM or LUNA 25 and Chandrayaan 3.
Also payload, it puts huge constraints on the weight and size of the satellite.

[sanjaykumar]

The returns on near earth missions may be significant eg a full up Atlas launch can reach a payload to the moon within hours. But interplanetary missions have the intrinsic distance as the rate limiting step not rocket thrust.

[Amber G.]

FWIW: Some comment: Improving rockets is a good thing ... but "Improving rockets" need not help in reaching there "quickly"..
The time it takes for space probes to reach specific destinations can vary widely depending on their launch date, trajectory etc .. propulsion systems may make a difference but only a small amount.

The typical time it takes to reach the Sun-Earth L1 point depends on the specific mission and launch date. but typically, it takes several weeks to a few months to reach L1.

The travel time to Venus also varies depending on the launch date and the specific mission goals. On average, it takes about 3 to 6 months to reach Venus when using a direct trajectory from Earth to Venus.

(For missions that use gravity assists or other complex trajectories, travel times may vary --bigger rockets may make orbit calculation easier but do not make a drastic difference ..)

If the satellite leaves Earth orbit at a higher speed shouldn't it reach its destination early?
I agree that we have to calculate the optimum path as due to Venus' orbit most of the time the distance between Earth and Venus is higher. But during the launch window also speed will be a crucial factor. Like in case of Maven and MOM or LUNA 25 and Chandrayaan 3.
Also payload, it puts huge constraints on the weight and size of the satellite.

Bigger rockets, can allow bigger payload ...

But for *all* practical purposes, a rocket sent from earth to moon (and assuming it is to be captured into moon's orbit/landing) the fastest time is about 70 Hours ... as calculated by Newton.. (or Jules Verne's Fiction - based on Newton's math).

All Apollo missions took about 70-80 hours to reach moon's orbit after TLI... (These had *massive* Saturn rockets) Same with Russian missions which soft-landed or orbited the moon.

Only exception, I believe is Luna-1 which they just wanted to hit the moon.. and explode .... took about half that much time.
(This was in 1959 ... see Sudarshan's post in CY3 dhaga -- the stunt was the one that caused US to think about following the suit.. but US did not)

For Venus - typical (fastest) time, as I said was 100 days ...
(Here Newton's math come into play - power of rocket not that much --- at least for the time being - till we discover something entirely new ). .. (We can probably half that time if we want to burn and crash .. but not if we want to go there and orbit the other planet)

[Najunamar]

AmberGji, is it because by the time you accelerate to such a high velocity you will overshoot the planet and to decelerate will require enormous amounts of fuel and time?

[Amber G.]

^^^ Sort of right , but I will explain it this way:
It is simple math (requires very elementary Newton's orbit math).--- this is very similar to using transfer orbit to put an sat from lower orbit to a higher orbit.

To go to moon, you need an ellipse whose perigee is close to earth (when TLI takes place) and apogee is near the moon (so it get captured).. All you need is the formula I gave for T (Time period of the orbit - and half the T as you are not going to return but get captured by the moon) for such an orbit.

The formula is here

Too much speed, you will pass moon with fairly high velocity in the orbit near the moon too.. and unless you have tremendous amount of fuel you can not get slow enough to be captured by the moon.

Only time if you just want to make a fly-by or want to crash on the moon, you can use high initial velocity..

[SSSalvi]

We need to improve our rocket's thrust quickly.
How long will it take for us to reach Venus If we use the slingshot method?
Aditya l1 takes 109 days to cross 1.5 million km, Venus is 61 million km away.
The central government should, first of all, assign funds for NGLV.

Not much change ..
For reaching L1 104 days after last EBN.
This time will more or less be same for going out of Earth Gravity ( SOI ). Afterwards it is the trajectory plan that will decide the duration to destination because once out of Earth SOI, you become a part of solar system and you can't change anything except a good planning.

The most you can reduce is successive increasing of Apogee to reach SOI.

[Piyal.g]

Thanks, all for clarifying the point for me.
That is why space is so interesting for me, you can keep on learning new things your whole life.