Friday, September 1, 2023

Of Course It's Flying at Night

Fresh on the heels of their successful Chandrayann-3 mission, the Indian Space Research Organization will be launching a probe to study the sun.  The mission, called Aditya-L1 is set to launch in the early morning hours Saturday - 2:20 AM US Eastern Time (if it doesn't launch that page is likely to say something else by the time you get to it).

It doesn't need to fly at night because it's not really going to the sun (that just might be the oldest joke I can remember).  The L1 in the mission name is where it's going: the L1 Lagrange point on the sunward side of Earth.  Aditya is Sanskrit for sun.  The James Webb Telescope as well the European Euclid telescope are on the opposite side of the Earth from L1.  Since the L1 point always is exposed to the sun, it's home to NASA's Solar and Heliospheric Observatory Satellite SOHO. The advantage of observing from L1 (actually an orbit around L1) is there are no lost observation periods due to occultations or eclipses.  I should point out that this drawing doesn't seem to show well that L1 and L2 are the same distance from earth, about 932,000 miles.  

Image credit to the NASA/WMAP Science Team.

The ISRO lists a large number of research objectives:

  • Study of Solar upper atmospheric (chromosphere and corona) dynamics.
  • Study of chromospheric and coronal heating, physics of the partially ionized plasma, initiation of the coronal mass ejections, and flares
  • Observe the in-situ particle and plasma environment providing data for the study of particle dynamics from the Sun.
  • Physics of solar corona and its heating mechanism.
  • Diagnostics of the coronal and coronal loops plasma: Temperature, velocity and density.
  • Development, dynamics and origin of CMEs.
  • Identify the sequence of processes that occur at multiple layers (chromosphere, base and extended corona) which eventually leads to solar eruptive events.
  • Magnetic field topology and magnetic field measurements in the solar corona .
  • Drivers for space weather (origin, composition and dynamics of solar wind )

To accomplish these, the probe brings seven instruments.  

  1. Visible Emission Line Coronagraph (VELC)    
  2. Solar Ultraviolet Imaging Telescope (SUIT)
  3. Solar Low Energy X-ray Spectrometer (SoLEXS) 
  4. High Energy L1 Orbiting X-ray Spectrometer (HEL1OS) 
  5. Aditya Solar wind Particle Experiment (ASPEX) 
  6. Plasma Analyser Package For Aditya (PAPA) 
  7. Advanced Tri-axial High Resolution Digital Magnetometers


The article at that got me started researching this mission has much more coverage of the various research targets.  After hundreds of years of continually-refined observations, the sun still has lots of mysteries available for study.  The first one they mention is what they call the sun's hottest mystery: the corona is much hotter than the surface of the sun although they are in constant contact.  The corona can reach 2 million degrees Fahrenheit. The photosphere, around 1,000 miles below it, has an average temperature of around 10,000 degrees F, meaning the sun's outer atmosphere is about 200 times hotter than its surface!  

The obstacle to observing the corona from Earth is how much brighter the photosphere is than the corona.  It's typically only visible during a total solar eclipse.  An alternative that works better in space than on the ground is a corona graph, an instrument on a telescope that blocks out the sun so the corona can be seen.  It works better in space because there's no airborne junk to brighten around the image.  Or so I've read.  Aditya-L1 carries one, the first instrument in that list. 

Here's wishing luck to the ISRO and Aditya-L1. 


  1. Good on India. The more SCIENCE, the better. Especially if it's done by Not-ChiComs.

    Next up is Japan. With their next launch, which has a lander that lands very weirdly, has no traditional landing legs as it's designed to fall on it's 'side,' after almost landing on thrusters.

    That and a new X-ray telescope.

    1. If you're to mention political ideaogy, you realize that India is a socialist country, yeah?

    2. And so are we. National Socialists that is.

      India may be socialist, but they aren't the CCP. They're socialist like Western Europe.

  2. Good to see other Space Agencies doing this. NASA *can* do it, and do it exceptionally well, but they get very bogged down in Political Crud from time to time.

    1. And the giant sucking sound of NASA's budget is SLS, yet another outdated boondoggle...

  3. good catch on the Lagrange diagram being not correct. Aditya-L1 successfully launched, en route to L-1. Guessing Aditya-L1 will talk with Indian Deep Space Network. India sited their network near Bangalore, not in the desert. Doesn't rain interfere with satellite communications? You mentioned always sunny at L-1 but not so much at Bangalore.

    1. I was looking at the Lagrange diagram and kept telling myself it had to be an optical delusion. Finally, I opened it in MS Paint, drew a line from the L1 dot to the Earth, and then moved the line to the other side, sure enough, it was well short of L2.

      Anyway, rain issues with Satcom depends on the frequency. C-band gets less fade than Ku and S-band gets less than C. If they're smart (and they are) it's manageable.

  4. Is it me, or is L1 and L2 starting to get crowded?

    1. Let me put on my Ackchyually guy shirt. OK, ready. Things don't stay at Lagrange points, they orbit around them. How crowded they are depends on the orbits and how similar they are.

      It seems to me that someone, some ... group ... should be monitoring what's out there and what orbits they're in to see if they're getting crowded, but one of the attractions of those points is that they're stable and require fewer regular maneuvers to stay in their orbits. To me, that also implies that debris / crap might settle into those areas. increasing the chances for collisions. Which says you might not want to get very close to the actual point and orbit kinda far away.

      I don't know all the tradeoffs involved.

    2. Of course I'm talking about the orbits, SiG - but the orbits aren't particularly stable, course corrections need to be dialed in occasionally. Look at the gravitational contour maps of these particular points, you will see that even small orbital deviations can cause the craft to "fall off the mountain". Easy to do with the constant solar pressure...