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

[disha]

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.

Then why is ISRO going with pocket rockets like SSLV? And RLV? And for Aditya L1, PSLV is used inspite of ISRO/India having GSLV Mk2 and Mk3. So what gives?

Rocket thrust increase is necessary for several reasons, but with deep space missions, all and every available capacity to launch will be used to pack instruments. And we will be back to Oberth maneuvers. The extra jumps around Earth.

Taking a step back and looking at Comm sats. The rocket capacity to launch comm sats or met sats topped off at most 5000 Kg to GTO. Rockets with 10T to GTO now take couple of sats together.

So what happened? There was a race to get larger rockets to take larger payloads to orbit. And it topped out at 10T to GTO. In fact, the race is now the other way, that is to launch pocket rockets like SSLV.

There is a reason for *not* going with larger rockets. They have long lead times from plan to launch and then they wait for the knapsack to fill up. For example, if you have a launch capacity of 10T and you have two Comm Sats at 4T each, you have wasted a capacity of 2T (which is significant). Or you plug in a 2T payload to optimize your launch capacity but then your launch plan becomes complicated.

And the way things are going, the comm sats are getting smaller and smaller. The met sats are getting smaller. The nav sats are getting smaller. Hence the race is to launch pocket rockets like SSLV. All solid, fast turn around time. Cheaper.

So what is driving the need for higher thrust capacities? Ability to launch humans to space? That can be done by RLV. Ability to launch science payloads to Moon? Or Mars? Or Human moon missions? Those missions require a deep commitment from the nation over a period of several decades. And that will also mean requiring making several sacrifices. And that is a conversation for a separate thread.

Of course, there is the human need for instant gratification of sending a satellite to deep space and it reaching there immediately, maybe at the speed of light. That need will not be only secondary, but tertiary or remote.

Put it this way, Oberth maneuver will not go away.

Of course, given Russian and Chinese competition, particularly the later one is not necessarily driven by science, the ask for larger thrust rocket must be there. Since it does take a long time to build and qualify one. And there will be costly missteps along the way, for example the SCE.

---

Aditya L1 is great technical challenge. It will be interesting experience to not just reach there, but stay there. So if you can do Oberth maneuver(s) and keep a larger amount of fuel handy, your time at station can be more. Hence even if you have say 100T capacity to launch to GTO/L1/L2, you might want to get the most out of your precious payload and that can be accomplished by keeping it there for the longest duration. Like ISRO did with MOM.

My dream will be to see, Post Aditya L1, India launch Astrosat L2, which will be actually an infrared space telescope peering deep to search for habitable planets or even study trojan bodies of the Sun-Jupiter systems.

[SSSalvi]

I am really alarmed.
No update of A-L1 orbit parameters aka TLE.
Also ISRO not sharing Orbit parameters on Horizons.
Does it have something to do with ISRO- ESA tie-up for Precision orbit determination methodology?

[Amber G.]

^^^ Wish Orbit parameters were shared with JPL/Horizons (and on timely basis). But FWIW, even with CY3, the horizon updates some times lagged a few days after a few events/burns. ( OTOH it also started supplying ephemerides for both Vikram and PM of CY3)

[SSSalvi]

That was expectation..
Planned trajectory of CH3 was available on Horizons at least a month before launch. Figures I posted midway in CH3 dhaga / Page4 were actually drawn before launch.
Subsequently ISRO updated it with factual parameters ( Step by step ) as the EBN operations continued.

Celestrak is independent of NASA ( at least apparently ), doing tracking of bodies, but they too have not updated info. CH3 was updated till Last EBN, till it was Earth Bound.

[Amber G.]

,, 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.

FWIW: A comment: From what I know - the Atlas V rocket, developed by ULA, is a reliable and well-established launch vehicle used primarily for sending payloads into Earth orbit and launching spacecraft on interplanetary missions.

The typical (fastest time) ( time it takes for a spacecraft to reach the Moon after Trans-Lunar Injection (TLI)) can vary depending on several factors but is around 70-90 Hours (3-4 days)

Apollo missions typically took about 3 to 4 days (72 to 96 hours) to travel from Earth to the Moon after TLI.

The Luna missions conducted by the Soviet Union and later Russia took around 3 to 4 days, similar to Apollo missions,
( some took longer.)

China's Chang'e missions to the Moon, such as Chang'e-3 and Chang'e-4, also took several days to reach the Moon after TLI. (The travel time is similar to the Apollo missions, typically around 3 to 4 days.)

Various other lunar missions by different countries and space agencies have followed a similar timeline of several days to reach the Moon after TLI.

Exceptions, as I said before, are impacts (or fly bys) which took , in some cases (at the fastest) around half that much.

Luna-1 took 34.5 hours - one of the fastest. Some probes from US (again crash or fly-by) took around 2.5 days(50-60 hours)..

----
Some note-worthy (approx timing)
Luna 2 (Soviet Union): Luna 2, also known as Lunik 2, ( 36 hours to impact the Moon's surface -1959)

Ranger Program (United States): NASA's typically took a few days (approximately 2.5 to 3 days) to reach the Moon after TLI. (1060's_, (Again impact or fly-bys)

SMART-1 (European Space Agency): SMART-1, took about 13 months to reach lunar orbit (2004), ( SMART-1 was an ion propulsion spacecraft, which allowed it to use less propellant but required a longer travel time)

Chandrayaan-1 (India): India's Chandrayaan-1 (2008, used a combination of gravity assists and propulsion to reach lunar orbit. It took approximately 5 days to reach the Moon after TLI.

Chang'e Missions (China): China's Chang'e missions, including Chang'e-1, Chang'e-2, and Chang'e-3, typically took several days to reach the Moon after TLI, similar to the Apollo missions. The travel time was in the range of 3 to 4 days.

(Math is not complicated -- Even in Jules Verne's fiction it took about 3-4 days -- (Jules Verne had a physicist friend who did this math -- known from Newton's time -- (Look at my post in CY3 for T)

[Amber G.]

Aditya-L1, destined for the Sun-Earth L1 point,
takes a selfie and images of the Earth and the Moon.

[sanjaykumar]

New Horizons took 8.5 hours to flyby the moon.

[Amber G.]

New Horizons took 8.5 hours to flyby the moon.

Assuming it is not a trolling type one liner..
(Please keep reading, if interested in actual science):

No, the New Horizons spacecraft did not take 8.5 hours to reach the Moon. (passing moon's 'orbit' is not the same thing as 'flyby the moon') New Horizons was launched by NASA in 2006, with the primary mission of studying Pluto and its moons. It completed a flyby of Pluto and its system in July 2015.
The journey to Pluto took New Horizons about 9.5 years, traveling a distance of approximately 5 billion kilometers) to reach its destination.



New Horizons is a NASA spacecraft designed primarily for the exploration of Pluto and the Kuiper Belt, not for missions to the Moon. Some key details :

New Horizons was launched with the primary mission of studying Pluto, its moons, and the environment of the Kuiper Belt, which is a region of the solar system beyond Neptune populated by small icy objects. The goal was to provide the first close-up images and data of Pluto and its system.

New Horizons successfully conducted a flyby of Pluto in 2015. During this historic encounter, it came within 12,500 Km of Pluto's surface, providing detailed images and scientific data about the dwarf planet and its five known moons.

After the Pluto flyby, New Horizons continued its mission by studying other objects in the Kuiper Belt. It conducted a flyby of a Kuiper Belt object nicknamed "Arrokoth" few years ago . This encounter provided valuable insights into the formation and evolution of these distant objects.

New Horizons is equipped with a suite of scientific instruments, including cameras, spectrometers, and particle detectors, designed to capture images, analyze composition, and study the environment of its targets.

Distance and Speed: New Horizons traveled a remarkable distance to reach Pluto and the Kuiper Belt, covering approximately 4.9 billion kilometers over the course of its journey. It is one of the fastest spacecraft (probably not the fastest) ever built, reaching speeds of up to 16.5 Km/s ( Compare this to CY3's speed at TLI about 10-11 Km/sec)

(The maximum speed was arrived after gravity assist fly-by of Jupiter)

New Horizons was not sent to the Moon; its primary mission was to explore Pluto and the Kuiper Belt.

Yes, horizons was launched atop an Atlas V rocket. The launch provided the spacecraft with the initial velocity needed to escape Earth's gravity..(and escape velocity needed to leave earth's orbit due to sun's gravity -- see my messages in CY3 threads about physics of this. The escape velocity is ~ 42 Km/s but as earth's velocity is around 30Km/s -- at good position, one needs only about 12 Km/s ... Atlas type rockets can provide up to 16 Km/s or so ).

At the speed of 16.5 Km/s, it can cover earth-moon distance in 7-8 hours, but it is silly to translate this into "did fly by to moon in 8.5 hours" .... If you take CY3's velocity at TLI, it would cover earth-moon distance in 9 hours -- but that's sort of silly to claim that. /sigh/
To be clear, AFAIK: New Horizons launched directly from Earth and did not use any Moon fly-by or gravity assist during its journey.

( I think, this was probably copied from some popular/wiki type comment "only xyx hours to pass the Moon's orbit"
statement .. to be clear, passing moon's orbit is NOT the same thing as moon fly-by"

AFAIK also: The spacecraft's only gravity assist maneuver was performed at Jupiter in, 2007. This gravity assist from Jupiter significantly increased New Horizons' velocity and redirected its path toward Pluto.

[Tanaji]

It also depends on what the velocity is with respect to. Voyager 1 due to its Jupiter gravity assist is leaving the solar system at 17 km/s wrt the sun which I think is faster than New Horizons which launched at 16 km/s wrt earth plus the relevant velocity component due to earths orbit but is now at 14 km/s I think.

Meanwhile the Parker solar probe is way higher at 190km/s as it orbits but thats a different metric altogether.

So it depends on what you are measuring.

[Tanaji]

On another note in terms of pure science done , Aditya will fo more of it than CY3 inspite of the latter getting the attention.

Obviously the engineering aspect is a different story..

[SSSalvi]

The image by ISRO is Earth centric so the Large Inflexion before entering L1 space is a bit confusing.



Plotted in a Sun centric view for Sept 23 to Feb 24 period.

Yellow Dot is SUN... White Curved line is Earth orbit around Sun ... Blue line is the path of L1 ....

Multi coloured line is path of AdityaL1 .. Each colour depicts one month period.

In First view Sept is near the observer. 2nd view is with Feb near observer.

Caution: Scale is not same in all the planes. Z axis is highly exaggerated.

[nitzter]

Plotted in a Sun centric view for Sept 23 to Feb 24 period.

Yellow Dot is SUN... White Curved line is Earth orbit around Sun ... Blue line is the path of L1 ....

Multi coloured line is path of AdityaL1 .. Each colour depicts one month period.

Highly appreciate this... Always wanted to view the complex trajectory in correct perspective (keeping scale aside)

My thoughts -
1. Aditya was launched into a low inclination orbit (19.20°) at 1pm IST.
2. India was sun facing while, half way across the world, the northern tip of South America became the first perigee (PS4 cutoff above the region).
3. The satellite would perform the transfer, after final earth burn, into a slightly inward tangent using almost the same inclination as per point 1.
4. The satellite is bound to come back into the folded xy plane of Earth's revolution. In other words, Aditya would go far away from Earth and come back following it's elliptical trajectory.
5. The slight inward transfer would decide if the satellite gets sufficiently near to the L1 point in the z axis when it falls back to the 'perigee' as per point 4.
6. Again, the low inclination would provide a soft angle of approach at L1 and hence requires less fuel to deccelerate from the perigee speed and achieve the insertion (with an inflection).

[Amber G.]

Modi and Biden talks about Aditya L1 and CY3 in their joint statement - my post in CY3 dhaga

7. President Biden congratulated Prime Minister Modi and the scientists and engineers of the Indian Space Research Organisation (ISRO) on Chandrayaan-3’s historic landing at the south polar region of the Moon, as well as the successful launch of India’s first solar mission, Aditya-L1. Having set a course to reach new frontiers across all sectors of space cooperation, the leaders welcomed efforts towards establishment of a Working Group for commercial space collaboration under the existing India-US Civil Space Joint Working Group. Determined to deepen our partnership in outer space exploration, ISRO and the National Aeronautics and Space Administration (NASA) have commenced discussions on modalities, capacity building, and training for mounting a joint effort to the International Space Station in 2024, and are continuing efforts to finalise a strategic framework for human space flight cooperation by the end of 2023. India and the United States also intend to increase coordination on planetary defence to protect planet Earth and space assets from the impact of asteroids and near-Earth objects, including US support for India’s participation in asteroid detection and tracking via the Minor Planet Center.

[Roop]

I am really alarmed.
No update of A-L1 orbit parameters aka TLE.
Also ISRO not sharing Orbit parameters on Horizons.
Does it have something to do with ISRO- ESA tie-up for Precision orbit determination methodology?

SSSji, the following is not a rhetorical question, please help me understand: why are you alarmed?

Does it have something to do with ISRO- ESA tie-up for Precision orbit determination methodology?

Let us assume, for the sake of argument, that the asnwer to this question is Yes. Given that assumption, why is this a cause for alarm? TIA.

[Amber G.]

^^^ ISRO-ESA tie-up notonly for precision orbit determination (software, helping each other and learning from each other) .. along with NASA and others they support each other as they have radio antennas spanning the whole globe.

This is a good thing. See today's Modi/Biden joint statement --- It shows how important and productive this kind of cooperation is:

7. President Biden congratulated Prime Minister Modi and the scientists and engineers of the Indian Space Research Organisation (ISRO) on Chandrayaan-3’s historic landing at the south polar region of the Moon, as well as the successful launch of India’s first solar mission, Aditya-L1. Having set a course to reach new frontiers across all sectors of space cooperation, the leaders welcomed efforts towards establishment of a Working Group for commercial space collaboration under the existing India-US Civil Space Joint Working Group. Determined to deepen our partnership in outer space exploration, ISRO and the National Aeronautics and Space Administration (NASA) have commenced discussions on modalities, capacity building, and training for mounting a joint effort to the International Space Station in 2024, and are continuing efforts to finalise a strategic framework for human space flight cooperation by the end of 2023. India and the United States also intend to increase coordination on planetary defence to protect planet Earth and space assets from the impact of asteroids and near-Earth objects, including US support for India’s participation in asteroid detection and tracking via the Minor Planet Center.

I have been following ISRO, NASA since 1960's .. have many colleges, friends, students in both places.. this kind of cooperation, which is better than it ever was, is good thing.

[Amber G.]

Highly appreciate this... Always wanted to view the complex trajectory in correct perspective

SSSalvi, Nitzter and others:
FWIW some comments:


(For those, who are not afraid of math, though I am going to keep it simple - assuming basic knowledge of orbital mechanics. Ignore if you wish)

Please read it carefully - if doubt, check out any standard text-book or ask somebody good in physics.

---
If you look at the orbits from an inertial frame (say from near the ecliptic pole above the sun) perspective and keep the same scale in all directions so not to exaggerate ripples - the orbit of Aditya L1 will look like ordinary heliocentric orbits -- small (noticeable only if you look very carefully) perturbations.

For perspective, this is not surprising. we look at moon's orbit - everyone draws in the text-books. In inertial frame, it will not look much different than earth's orbit going around the sun. No loops around earth ... just some small perturbations in an ellipse. (IMO about 99% of the people get it wrong - the moon's orbit, as seen from sun, has no loops etc..) (Scientists call earth-moon system as twin-planets -- not a sat going around earth..)

(Mathematically, even though moon is closet to earth (bout 400x) the sun is about 333,000 times more massive, the gravitation force on moon due to sun is about twice than due to earth) (Many people consider moon going around earth in the same way as a sat going around earth.. not true in the sense that for moon (to calculate its motion around earth), you can not ignore sun's gravity --- in fact it is twice as much as that due to earth)

----

Halo orbits are a type of Lissajous orbits. For those electrical engineers (or physicists) familiar with Lissajous pattern, this is circular-ish orbit is just showing a 1:1 Lissajous pattern.


These Lagrange-point orbits are really orbiting around the sun , in a way that's resonant with the earth's time period. In the Earth-Sun system, Aditya L1 (hopefully - soon it will be doing its thing) will be in Heliocentric orbits (orbits around the Sun) about 1% closer than the Earth's orbit around the Sun. (For L2, it is 1% farther)

The Earth's gravity is weak there, but strong enough to "tug" the satellites along a little faster or slower to keep them synchronized.

----

When you do rotating frame and move with the Earth, their motion appears to be around the L1 from your point of view in the rotating frame..

"Rotating frame" is mathematically, relatively, a difficult subject..

Mathematically, when doing calculations for a simplified Circular restricted three body problem(CRTBP - check out any good text book) the equations become easier when you use the rotating frame.

In an inertial frame, those satellites will appear to drift slightly up and down, making one full cycle roughly twice a year. In the rotating frame only, that motion looks like an orbit around, or at least associated with, the Lagrange point.

That motion has a "horizontal" or left-right component, and a "vertical" or up-down component. (Hence, physicists think of them as Lissajous patterns)

In some cases, this CRBP motion is large enough amplitude, those motions can have the same period, and so the orbit will appear to be closed, cyclic, and periodic in the rotating frame. Orbits in this subset are called Halo Orbits.

(BTW there are plenty of orbits in this family where the horizontal and vertical motion do not have the same period, and so they will appear to make a criss-cross or Lissajous figure in space viewed in the rotating frame. These are called Lissajous orbits)

From L1's case Halo orbits are used because they tend to circle around the Sun-Earth axis and avoid radio interference and power outages due to eclipsing of the solar panels.

Hope this is useful.. (I know more physics/math -- very rarely covered in most popular articles but hope it increase some basic understanding )

[juvva]

is it possible to use aditya l1 as a radio relay for any future indian lander missions to the far side of the moon ?

[srin]

For missions to far side of the moon, you'd want a relay at the earth-moon L2 point. Aditya L1 is going to be in Earth-Sun L1 point, which could be on the other side of earth for sometime (depending on orbital position of moon).

[juvva]

same would be the case with L2 , when the moon is on the sunward side of earth ?
am i missing something here ?


added later:

ok i think i got it, it is the L2 point of the earth-moon system, not L2 point of the sun-earth system.

[putnanja]

Aditya-L1 completes 4th Earth bound maneuvre (EBN#4), to begin journey to final destination on September 19

From ISRO facebook page and Twitter:

Aditya-L1 Mission:
The fourth Earth-bound maneuvre (EBN#4) is performed successfully.
ISRO's ground stations at Mauritius, Bengaluru, SDSC-SHAR and Port Blair tracked the satellite during this operation.
ISRO's transportable terminal currently stationed in the Fiji islands for Aditya-L1 supports post-burn operations.
The new orbit attained is 256 km x 121973 km.
The next maneuvre Trans-Lagragean Point 1 Insertion (TL1I) -- a send-off from the Earth -- is scheduled for September 19, 2023, around 02:00 Hrs. IST

[srin]

Trans-L1 Injection successful
https://twitter.com/isro/status/1703876 ... wsrc%5Etfw

Off to Sun-Earth L1 point!

The Trans-Lagrangean Point 1 Insertion (TL1I) maneuvre is performed successfully.

The spacecraft is now on a trajectory that will take it to the Sun-Earth L1 point. It will be injected into an orbit around L1 through a maneuver after about 110 days.

This is the fifth consecutive time ISRO has successfully transferred an object on a trajectory toward another celestial body or location in space.

[Amber G.]

Aditya L1 had successfully performed a crucial Trans-Lagrangian Point 1 Insertion (TL1I) manoeuvre that put it on the Sun-Earth L1 point trajectory

The spacecraft has travelled beyond a distance of 0.92 million Kilometers from Earth, successfully escaping the sphere of Earth's influence. It is now navigating its path towards the Sun-Earth Lagrange Point 1 (L1).

This is the second time in succession that ISRO could send a spacecraft outside the sphere of influence of the Earth, the first time being the Mars Orbiter Mission.

[Ashokk]

Aditya’s beyond Earth's influence; URSC software key to knowing its ‘past, present & future’, staying at vantage point

BENGALURU: India’s first solar space observatory, Aditya-L1, which has travelled beyond a distance of 9.2 lakh kilometres from Earth, successfully escaping the sphere of Earth's influence, is heading towards a location 1.5 million-km away from Earth, with Isro keeping a close eye on its journey.
However, reaching that destination isn’t the only challenge Adityafaces. Staying there is also tricky.
To ensure it gets to its destination and stays safely in orbit, Isro needs to know exactly where their spacecraft “was, is and will be”.
This tracking process, called ‘orbit determination,’ involves using mathematical formulas and specially developed software by Isro’s UR Rao Satellite Centre (URSC), Isro chairman S Somanath told TOI.
Where Aditya’s going
When one large mass orbits another, their gravitational forces and orbital motion interact to create five equilibrium points where a spacecraft can operate for a prolonged period of time without having to use a lot of fuel. These locations are known as Lagrange points. Aditya-L1’s final destination will be one of the five Lagrange points in the Sun-Earth system.
Also known as libration points, Lagrange points are unique locations in space where the gravitational force of two massive bodies (like Sun and Earth) precisely equals the centripetal force required for a small object (like spacecraft) to move with them.
L1, where Aditya will go, is particularly significant because it is situated between the two primaries (Sun and Earth), making it an ideal location for spacecrafts because they allow continuous observation of primary bodies, continuous communication with earth and an unobstructed view of celestial bodies.
These orbits are well-suited for scientific missions like Aditya which will act like a solar observatory around L1 and communicate to Earth.
The challenge
According to the European Space Agency (ESA), L1 is one of the ‘unstable’ Lagrange points and keeping a spacecraft exactly at the L1 point is practically impossible.
“Instead, spacecraft enter orbit around L1 as if the Lagrange point were an ‘invisible planet’. Even so, due to the instability of this orbit, small trajectory errors will grow quickly. As a result, spacecraft must perform ‘station keeping’ manoeuvres roughly once a month to keep them in the correct orbit.”
Somanath said while L1 is an unstable point, the instability is very mild and spread over a long period of time making it still the best place to be for a spacecraft. “L3 and L4 are much more difficult, for instance.”
“...That said, if we aren’t careful with regard to orbit determination then the spacecraft can diverge. While it can be brought back, the fuel penalty will be higher,” he said.
L1 & software
Theoretically, L1 is a constant point. It is a geometrical point that one gets when one connects the Moon, Sun and Earth.
Although L1 is theoretically between two objects, when it gets influenced by other bodies, the Moon for instance, it becomes a multi-body sphere. And depending on the movement of these bodies, there are changes Isro will need to account for with time.
“The halo orbit Aditya-L1 will be in is a vague orbit. It’s not like rotating around a single point. It is rotating around a vast area that is a three-dimensional orbit. Therefore, the need was for a multi-body computational programme to find out the trajectory of these bodies and the spacecraft. For this, Isro has designed and developed new orbit determination software for Aditya-L1,” Somanath said.

[Amber G.]

IT Kanpur conducted a 3-day workshop to train 50 selected final-year undergraduate (UG), MSc, and PhD students in the utilization of upcoming data from Aditya L1 Mission. It covered various in class and hands on sessions, and lectures, by eminent scientists and experts ..

Mission is expected to reach L1 Point in another 18-plus days...Per, ISRO Chairman S Somanath everything is performing satisfactorily

Meanwhile The X-ray Polarimeter Satelllite (XPoSat), designed to study the polarization of cosmic X-rays will be launched in December.

[SSridhar]

Solar mission: Aditya-L1 undergoes trajectory correction - ToI

Several days after it escaped the Earth’s sphere of influence, India’s first solar space observatory, Aditya-L1, underwent a Trajectory Correction Manoeuvre (TCM). The Spacecraft is healthy and on its way to Sun-Earth Lagrange Point-1 (L1) 1.5 million-km away from Earth.

The TCM, originally provisioned, was performed on October 6 for about 16 seconds, Isro said on Sunday, adding that the move was needed to correct the trajectory evaluated after tracking the Trans-Lagrangian Point-1 Insertion (TL1I) manoeuvre — an operation that put the spacecraft in its path to the final destination — performed on September 19, 2023.

“TCM ensures that the spacecraft is on its intended path towards the Halo orbit insertion around L1. As Aditya-L1 continues to move ahead, the magnetometer will be turned on again within a few days,” Isro said.

[Amber G.]

HEL1OS captures first High-Energy X-ray glimpse of Solar Flares

- During its first observation period from approximately 12:00 to 22:00 UT on October 29, 2023, the High Energy L1 Orbiting X-ray Spectrometer (HEL1OS) on board Aditya-L1 has recorded the impulsive phase of solar flares.

The recorded data is consistent with the X-ray light curves provided by NOAA's GOES.

- Commissioned on October 27, 2023, HEL1OS is currently undergoing fine-tuning of thresholds and calibration operations. The instrument is set to monitor the Sun's high-energy X-ray activity with fast timing and high-resolution spectra.
- HEL1OS data enables researchers to study explosive energy release and electron acceleration during impulsive phases of solar flares.

HEL1OS was developed by the Space Astronomy Group of the U. R. Rao Satellite Centre, ISRO, Bengaluru.



Link:https://www.ursc.gov.in/hel1os.jsp

--- For fun, saw the above with appropriate emojis ..


HEL1OS became active on October 27, 2023, and it's currently being adjusted for accuracy . It's designed to closely watch high-energy X-rays from the Sun , helping scientists study powerful solar flares and how they release energy and accelerate electrons .

[SSSalvi]

The sensor obviously is not yet calibrated ( Notice the vertical units ARB for arbitrary ) but it clearly shows a fast response time as compared with the older sensors on other probes.

In the post by URSC, they mention a very strong burst recorded at 1300 Hrs. They have ( rightly ) not disclosed at this time as they may want to hold iAt back till they present it fresh in some international seminar.

BTW, from where did they start their observations on A-L1 route to its home? Hold on for some time.. will post the full road to Home and also the details of Home HALO orbit for BRF fraternity before I publish on my YT channel.

[SSSalvi]

Journey of ADITYA L1 to Halo orbit and the Halo orbit itself:
( Sorry for a longish post .. but I am helpless )
( We will use ADI to refer to ADITYA_L1 )
With the capability of PSLV, maximum velocity that could be provided to ADI was about 9.7 kms/sec.
To break Earth's gravity to reach L1 point the escape velocity is 11.2 km/sec.

This velocity increase was achieved by successive increase of Apogee by firing thrusters at Perigee EBN#1, EBN#2,EBN#3 and EBN#4.

List of EBNs and orbits ( Perigee Height X Apogee Height ) achieved after each:

1. Launch orbit : 233Km X 19470 Km ( Sept 2 ) 2. After EBN#1 : 245 Km X 22459 Km ( Sept 3 ) 3. After EBN#2 : 282 Km X 40225 Km ( Sept 5 )
4. After EBN#3 : 296 Km X 71767 Km ( Sept 10 ) 5. After EBN#4: 256 Km X 121973Km ( Sept 15 )

Other operations carried out on ADI :

1. Sept 30 : ADI escapes SoI of Earth's gravity;
2. Oct 8 : Trajectory Correction Maneuver ( TCM ) done to precisely bring the Spacecraft to its planned trajectory.
3. Nov 7 : HEL1OS equipment test starts and captures a Solar flair.
4. Around 7th January 2024 a Halo Orbit Insertion Maneuver may be carried out by ISRO.

Figure on below shows the path ( White Trajectory ) of ADI from Launch ( 2nd Sept 2023 to 17th March 2024 ) as published by ISRO on NASA's Horizons website. Earth is at the intersection of axes. ADI started its journey from near the origin.
The BLUE ( Z ) axis is Celetial North South axis passing through the centre of Earth. RED ( X ) axis is the Equinoxes joining line ( Also the line on which Equator and Ecliptic cut each other. ), Y axis is orthogonal to X and Z axes.

Initial orbit raising raised the orbit and after final EBN#4, it started its journey almost parellel to -X direction.
Next, For clarity we remove axes in next figure and color the ADI path pink and mark various events as they happen on the way. We also add the path of L1 around Earth as it rotates around Sun.



Same situation we see a little from South and add corresponding time tags on L1 path ( Green ) also which allows us to imagine the relative position of ADI and L1 at a monthly interval.



We notice that ( we are not using scientific terms, but just relative description )

1. at SoI point the ADI is south of L1 and it travels northwards
2. Around 1st Dec it crosses over to south of L1 path BUT, it is almost farthest Left of L1.
3. Slowly ADI comes nearer to L1 and on 7th Jan it is nearest to L1.
4. As time passes, around mid February, ADI crosses over from South to North of L1 path. However, again both are farthest from each other and ADI is Right of L1.

It is difficult to visualise the path of ADI w r t L1.

For that we attempt to continuously rotate our xyz axes around Z axis, so that L1 ( and the Sun behind it ) are always pointing to the '-x' direction of new xyz frame.

( Let me confess : For the FIRST time in my life I found that one of the 1st theorem I had learnt in Co-ordinate geometry viz. Rotation of axes has a utility factor.. otherwise like many other things I was assuming it to be a useless learning in school/college !! )

After we apply that ( Rotation angle as a function of Time difference at every point ), Viola, we get the following :



In this figure Sun is away from viewer along -X direction ( Red axis ) and L1 ( Green dot ) is on the line joining Earth ( 0,0,0 ) and Sun.
Next, we hide axes and initial travel of ADI upto SoI exit point.

Before we explore further this elliptical orbit, a small clarity. Lets look to the path from Left side... We can clearly see a small but sure change in the path midway from SoI exit and Ecliptic crossing.. That is where around 7th Jan2024, ISRO will insert the ADI into its intended Halo orbit.
So what you see on upper portion in this figure is its journey to the intended orbit and from that point onwards is a part of the actual Halo orbit.

We next extrapolate the Halo Orbit path to full orbit. Here, Green portion depicts trajectory before Halo insertion and Pink portion After Halo insertion, and over it we superimpose the theoretical complete Halo orbit. ( Dashed Pink in lower image )

Apparently this looks to be a simple elliptical orbit ... B U T it is a highly deceptive shape when we see it in 3 dimension.
Let's add the axes frame with,
Earth at origin ( 0,0,0 ) and
X axis aligned with SUN-EARTH line ( Sun in -X direction ) and
Z axis to Celestial North.
Lagrange1 point is -1.5 Million Kms on X axis and Sun is at -1AU from Earth.
Let's look to Halo orbit from 3 orthogonal positions shown by arrows in adjacent figure right below.



The same Halo orbit looks different from 3 directions as shown in the figure below:


The reason why we see 3 shapes is that the Halo orbit is NOT a FLAT ellipse but is a 3 dimensional figure like a Shell. Especially the curvature in view along Y axis is totally unexpected.
Size of the Halo orbit and other essential details are in the diagram below.



Last 2 entries of subtended angles are of special interest to communications fraternity.

It answers the common question that these people ask: How will the communication take place when there is a Sun radio noise is behind the satellite?

Sun disc is about half a degree across but the ADI orbit is at least 2 degrees away from Sun.

So when the Earth bound antenna is pointed to ADI ( which is in the orbit path ), the Solar noise does not enter the antenna because its beamwidth is less than 0.25 degrees and so the data carrier does not get corrupted with Solar noise.

[Vayutuvan]

SSSalvi ji, very nice post and great visuals.

[SSSalvi]

Aditya Solar wind Particle Experiment (ASPEX) payload onboard India's Aditya-L1 satellite switched on on 1st Dec2023 ... working normal.

https://www.isro.gov.in/Aditya-L1_ASPEX ... ments.html

[SSridhar]

Aditya captures full-disk images of Sun; can aid in understanding impact of solar radiation on Earth’s climate

The Solar Ultraviolet Imaging Telescope (SUIT) instrument on board Aditya-L1, India’s first space solar observatory, has successfully captured the first full-disk images of the Sun in the 200-400 nm wavelength range.

“These observations will help scientists study the dynamic coupling of the magnetised solar atmosphere and assist them in placing tight constraints on the effects of solar radiation on Earth’s climate,” Isro said.

SUIT captures images of the Sun’s photosphere and chromosphere in this wavelength range using various scientific filters. “SUIT was powered ON on November 20. Following a successful pre-commissioning phase, the telescope captured its first light science images on December 6,” Isro added.

Terming the images “unprecedented”, the space agency said they were taken using eleven different filters. “The images include the first-ever full-disk representations of the Sun in wavelengths ranging from 200 to 400 nm, excluding Ca II h (relating to chromospheric emission), which has been studied from other observatories,” Isro said.

Among the notable features revealed are sunspots, plage, and quiet Sun regions, providing scientists with pioneering insights into the intricate details of the Sun’s photosphere and chromosphere.

The development of SUIT involved a collaborative effort under the leadership of the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune. This collaboration included Isro, the Manipal Academy of Higher Education (MAHE), the Centre for Excellence in Space Science Indian (CESSI) at IISER-Kolkata, the Indian Institute of Astrophysics (IIA) Bengaluru, the Udaipur Solar Observatory (USO-PRL), and Tezpur University Assam.

[Amber G.]

Aditya L1 ,will Reach Its Destination, Lagrange Point 1 around First Week Of January...( about January 7 th)

Meanwhile Video of the shutter on #AdityaL1's SUIT instrument opening and then closing!



The SUIT instrument is a telescope that takes pictures of the Sun in the ultraviolet spectrum.
video

Details , Pictures & Video

[Amber G.]

Journey of ADITYA L1 to Halo orbit and the Halo orbit itself:

Excellent post! Thanks.

To get some perspective on the figures he shared on the orbits - in x-y-z directions ..

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.

Now see the dimension given for the (halo) orbit -- to see how big they are..

[SSSalvi]

Amber G says in words... I, in drawing .

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.

Green line is Sun-L1 distance while Red line is L1-Earth distance.



Top portion shows larger view with Sun, while the lower part is a Zoomed view near Earth with Moon's orbit for comparison.

[SSSalvi]

Insertion in Halo Orbit planned on 6th Jan 24.
https://www.thehindu.com/sci-tech/scien ... 668378.ece

[Amber G.]

From Scientific American:
India’s Aditya-L1 Space Probe Heads for Gravitational ‘Island’

[Amber G.]

Aditya is all set to enter a halo orbit around Lagrange Point L1 today. Best wishes!
The critical thrust is just few hours away!

Just to refresh:

The payloads on Aditya

• Visible Emission Line Coronagraph (VELC) will study the solar corona and dynamics of coronal mass ejections.

• Solar Ultraviolet Imaging Telescope (SUIT) will image the solar photosphere and chromosphere in near ultraviolet and measure the solar irradiance variations.

• Aditya Solar Wind Particle Experiment (ASPEX) and Plasma Analyser Package for Aditya (PAPA) will study the solar wind, energetic ions and their energy distribution.

• Solar Low Energy X-ray Spectrometer (SoLEXS) and High Energy L1 Orbiting X-ray Spectrometer (HELIOS) will study the X-ray flares from the Sun over a wide X-ray energy range.

• Advanced Tri-axial High-Resolution Digital Magnetometers (MAG) will measure the interplanetary magnetic fields at the L1 point.

[SSSalvi]

Aditya-L1 in Halo orbit:


𝐈𝐧𝐝𝐢𝐚, 𝐈 𝐝𝐢𝐝 𝐢𝐭. 𝐈 𝐡𝐚𝐯𝐞 𝐫𝐞𝐚𝐜𝐡𝐞𝐝 𝐭𝐨 𝐦𝐲 𝐝𝐞𝐬𝐭𝐢𝐧𝐚𝐭𝐢𝐨𝐧!

Aditya-L1 has successfully entered the Halo orbit around the L1 point.

#ISRO #AdityaL1Mission #AdityaL1



https://twitter.com/isrosight/status/17 ... 1813088736


https://www.newindianexpress.com/nation ... 48536.html

[Amber G.]

From PM Modi:

India creates yet another landmark. India’s first solar observatory Aditya-L1 reaches it’s destination. It is a testament to the relentless dedication of our scientists in realising among the most complex and intricate space missions. I join the nation in applauding this extraordinary feat. We will continue to pursue new frontiers of science for the benefit of humanity.

Official Statement.. (Bolded emphasis is mine - signifying some technical aspects and details/understanding we discussed here)
Halo-Orbit Insertion of Aditya-L1 Successfully Accomplished

January 6, 2024

Halo-Orbit Insertion (HOI) of its solar observatory spacecraft, Aditya-L1 was accomplished at 16.00 Hrs (approx) on January 6, 2024 (IST). The final phase of the maneuver involved firing of control engines for a short duration.

The orbit of Aditya-L1 spacecraft is a periodic Halo orbit which is located roughly 1.5 million km from earth on the continuously moving Sun – Earth line with an orbital period of about 177.86 earth days. This Halo orbit is a periodic, three-dimensional orbit at L1 involving Sun, Earth and a spacecraft. This specific halo orbit is selected to ensure a mission lifetime of 5 years, minimising station-keeping manoeuvres and thus fuel consumption and ensuring a continuous, unobstructed view of sun.

The Aditya-L1 mission is an Indian solar observatory at Lagrangian point L1 for “Observing and understanding the chromospheric and coronal dynamics of the Sun” in a continuous manner. Placing the Aditya-L1 in a halo orbit around L1 point has advantages as compared to placing in a Low Earth Orbit (LEO):
It provides a smooth Sun-spacecraft velocity change throughout the orbit, appropriate for helioseismology.
It is outside of the magnetosphere of Earth, thus suitable for the "in situ" sampling of the solar wind and particles.
It allows unobstructed, continuous observation of the Sun, and view of earth for enabling continuous communication to ground stations.
Halo orbit insertion

The halo orbit insertion process commenced as the spacecraft crossed the XZ plane in the Sun-Earth- L1 rotating system, with the required orbital state. The insertion maneuver is essential to nullify the X and Z velocity components and attain the required Y-velocity in the L1 rotating frame for the required Halo orbit. The targeted Halo-orbit for Aditya-L1 is Ax: 209200 km, Ay : 663200 km and Az : 120000 km (The semi-axes of the 3-dimensional Halo orbit-refer figure).

The insertion of Aditya-L1 into this Halo orbit presents a critical mission phase, which demanded precise navigation and control. A successful insertion further involved constant monitoring along with the adjustment of the spacecraft's speed and position by using onboard thrusters. The success of this insertion not only signifies ISRO's capabilities in such complex orbital manoeuvres, but it but gives confidence to handle future interplanetary missions.

Aditya-L1 was designed and realised at UR Rao Satellite Centre (URSC) with participation from various ISRO centres. The payloads onboard Aditya-L1 were developed by Indian scientific laboratories, IIA, IUCAA and ISRO. The Aditya-L1 spacecraft was launched by PLSV-C57 on September 2, 2023 from SDSC SHAR, into an elliptical parking orbit (EPO) of 235.6 km by 19502.7 km. From here, Aditya-L1 embarked on an extraordinary journey towards the Sun-Earth-L1 Lagrange point, with the help of the onboard propulsion system, increased its orbital size progressively and moved toward L1 point. Five liquid engine burns (LEB) were executed during Earth orbit phase; gradually raised the apogee of the EPO in order to attain the desired trajectory with the fifth burn, known as the trans-L1 injection (TL1I) maneuver. The maneuver strategy is carefully devised to minimize incremental velocity addition (ΔV) for reaching the target L1 halo orbit while restricting the number of perigee passes to minimize the spacecraft's exposure to the high radiation Van Allen radiation belts. To address errors during, TL1I phase, a short burn of the engines, called TCM-1 was conducted on October 5, 2023, and another TCM-2 on December 14, 2023 to ensure compliance with Halo orbit insertion condition parameters. The spacecraft underwent a cruise phase lasting approximately 110 days to achieve the present condition prior to HOI targeted on January 6, 2024.

All the payloads were tested during the pre-commissioning phase and performance of all the payload is confirmed to be satisfactory.

The picture below shows the Halo orbit insertion process graphically in a two dimension picture. The Aditya-L1 spacecraft was moving from Earth towards the L1 point in the direction of Sun. The TCM1 &2 firing oriented the spacecraft toward the Halo Orbit, making it reach the HOI condition (which is a minimum fuel consumption condition) as on 6th January 2024 (Marked by the red dot). The final firing was done at this point, making the spacecraft align with the Halo Orbit. If the HOI manoeuvre was not conducted as done today, the spacecraft would have moved in the direction marked (Without HOI).

[Amber G.]

https://www.financialexpress.com/life/science-aditya-l1-isro-successfully-deploys-magnetometer-boom-on-board-spacecraft-3376096/

The Indian Space Research Organisation (ISRO) has successfully deployed the magnetometer boom on board the Aditya-L1 spacecraft. In space, it will measure the low-intensity interplanetary magnetic field.

On January 11, the six-metre-long magnetometer boom was deployed in the Halo orbit at the Lagrange point L-1, said the space agency. ISRO informed that the boom had been in stowed condition for 132 days since the Aditya-L1 liftoff.