Suramya's Blog : Welcome to my crazy life…

When we look at the photographs of the outer planets in our solar system, the planet Neptune stands out because of it’s striking blue color as shown in the photos taken by Voyager 2 back in 1989. (See below)

Photo of Neptune as taken by Voyager 2

In a new study just published in the Monthly Notices of the Royal Astronomical Society, researchers found that the color balance in Voyager was a little skewed that led to the planet appearing more blue than it actually is. Basically due to the way the images from Voyager were contrast enhanced to accentuate fainter features and better illustrate the atmospheric features of the planet the image released was bluer than what the planet actually looked like. They used observations of the planet taken from 1950 to 2016 along with data from the Hubble Space Telescope and the Very Large Telescope to create a more accurate representation of the planet’s color which is closer Uranus’s color than the vivid blue we are used to seeing. (See below)

Panels a and b show early images of the visible appearance of Uranus and Neptune reconstructed from Voyager 2 ISS images in 1986 and 1989, respectively, showing Uranus to be pale blue-green, and Neptune dark blue (PIA18182 and PIA01492, credit: NASA/JPL-Caltech).
Panels c and d show more recent reconstructions of the true colours of these planets, showing them to be more similarly coloured (credit: NASA/JPL-Caltech/Björn Jónsson)

From the Paper:

We present a quantitative analysis of the seasonal record of Uranus’s disc-averaged colour and photometric magnitude in Strömgren b and y filters (centred at 467 and 551 nm, respectively), recorded at the Lowell Observatory from 1950 to 2016, and supplemented with HST/WFC3 observations from 2016 to 2022. We find that the seasonal variations of magnitude can be explained by the lower abundance of methane at polar latitudes combined with a time-dependent increase of the reflectivity of the aerosol particles in layer near the methane condensation level at 1 – 2 bar. This increase in reflectivity is consistent with the addition of conservatively scattering particles to this layer, for which the modelled background haze particles are strongly absorbing at both blue and red wavelengths. We suggest that this additional component may come from a higher proportion of methane ice particles. We suggest that the increase in reflectivity of Uranus in both filters between the equinoxes in 1966 and 2007, noted by previous authors, might be related to Uranus’s distance from the Sun and the production rate of dark photochemical haze products. Finally, we find that although the visible colour of Uranus is less blue than Neptune, due to the increased aerosol thickness on Uranus, and this difference is greatest at Uranus’s solstices, it is much less significant than is commonly believed due to a long-standing misperception of Neptune’s ‘true’ colour. We describe how filter-imaging observations, such as those from Voyager-2/ISS and HST/WFC3, should be processed to yield accurate true colour representations.

It is facinating how much more there is to learn in the cosmos even about our own stellar neighbors never mind the whole wide universe out there with its infinite mysteries and grandeur.

Source: Neptune is more of a greenish blue than is commonly depicted

– Suramya

ISRO (Indian Space Research Organization) made a surprising announcement earlier this week about a new accomplishment by the Chandrayaan-3 Propulsion Module after the team managed to successfully return the propulsion module used by the spacecraft into a high orbit around Earth. This is a big deal and something only achieved by 3 countries before India (US, China and USSR).

This was not one of the planned missions for the module and was attempted when the team found that they still have over 100 kg of fuel in the PM available on the module for maneuvers. Its a credit to the precise planning and execution of the entire mission that the module still had extra fuel available for followup missions. So the orbit was modified over the course of a few months to move to an Earth orbit at about 1.54 lakhs kms (154,000 kms) allowing the module to complete an orbit every 13 days.

In order to continue SHAPE payload for Earth observation, it was decided to re-orbit the PM to a suitable Earth orbit.This mission plan was worked out considering the collision avoidance such as preventing the PM from crashing on to the Moon’s surface or entering into the Earth’s GEO belt at 36000 km and orbits below that. Considering the estimated fuel availability and the safety to GEO spacecrafts, the optimal Earth return trajectory was designed for October 2023 month.

First maneuver was performed on October 9, 2023 to raise apolune altitude to 5112 km from 150 km thus, increasing the period of orbit from 2.1 hrs to 7.2 hrs. Later, considering the estimate of available propellant, the second maneuver plan was revised to target an Earth orbit of 1.8 lakhs x 3.8 lakhs km. The Trans-Earthinjection (TEI)maneuver was performed on October 13, 2023. In thepost-TEI maneuver realized orbit, propulsion module made four Moon fly-bys before departing Moon SOI on November 10. Currently, propulsion module is orbiting Earth and crossedits first perigee on November 22nd with an altitude of 1.54 lakhs km. The orbit period is nearly 13 days with 27 deg inclination. The perigee and apogee altitude vary during its trajectory and the predicted minimum perigee altitude is 1.15 lakhs km. Hence as per current orbit prediction, there is no threats of close approach with any operational Earth orbiting satellites.

This test was a good way to prepare for future lunar missions where one of the mission parameters would be to bring back samples from the Moon to earth for study. The module’s expected lifetime was about 3 months and its already past that and still going on. Looking forward to finding out what other additional experiments we can run on it.

– Suramya

Source: Arstechnica.com: India reveals that it has returned lunar spacecraft to Earth orbit

The Aditya-L1 was launched successfully on Saturday and inserted into orbit as per the plan. This is India’s first mission to study the Sun, and is a natural next step (if you think about it) after a successful moon mission. The planned duration of the mission is 5.2 years.

Was talking to Jani yesterday and she asked what the L1 point was, and I had just assumed everyone knew what it was because I knew it. But then I realized that this is not common knowledge though more people are learning about it thanks to the coverage of the Aditya-L1 mission. Basically, the definition is as below:

Lagrange points are positions in space where objects sent there tend to stay put. At Lagrange points, the gravitational pull of two large masses precisely equals the centripetal force required for a small object to move with them. These points in space can be used by spacecraft to reduce fuel consumption needed to remain in position.

To put in a simpler way, this is a place between the Earth and Sun where the gravitational pull of the sun is cancelled by the gravitational pull of the Earth. There are multiple such points around the solar system. The L1 point is approximately 1.5 million km away from Earth (about 1% of the Earth-Sun distance)

Visual depiction of Lagrange Points, curtsy of ISRO

The Indian space program is shining because of their two back to back missions where very few other countries have succeeded in the past, so obviously we have folks in the western media claiming that the Chandrayaan-3 mission was faked and lots of editorials where ‘experts’ talk about how India should focus on feeding its poor instead of the space program. These folks need to take a closer look at their own countries and the state of their poor & the state of their infra instead of lecturing India.

That being said, not everyone responded in a racist way, plenty of publications covered the mission and were complementary about how much India has achieved in the past few years. Ars Technica did a pretty indepth and balanced walk through of India’s space programs and how it ranks against the other global powers.

Also, to those who from the UK who are asking for their ‘aid money’ back (which was actually investment money being shown as aid money), you are more than welcome to ask for it back after you pay back all the money the British Raj looted from India, and have returned all the stolen treasures being showcased in the British museum. Actually, why don’t we do this: deduct the money you claim to have sent for aid and then return the rest and then we can talk. Till then we will keep ignoring you.

Jai Hind.

– Suramya

After successfully landing Chandrayaan-3 on the Moon, ISRO is not resting on its laurels. Their next mission (Aditya L1) is on schedule to launch on 1st Sept 2023 and this will be the first space based Indian mission to study the Sun. The craft, named after the Hindi word for the sun, will be launched from the spaceport in Sriharikota using India’s heavy-duty launch vehicle, the PSLV, which will travel about 1.5 million km (932,000 miles). The craft will be placed in a halo orbit around the Lagrange point 1 (L1) of the Sun-Earth system, which gives it the advantage of continuously viewing the Sun without any eclipses or blockages. So far only 3 other countries/entities have successfully launched Solar probes: NASA (US), DFVLR (Germany), ESA (European Union). ISRO will be the 4th to do so.

Citizens are invited to witness the launch from the Launch View Gallery at Sriharikota by registering at their website. This is an awesome improvement in the process to visit the launch site. A few years ago when Surabhi and Vinit wanted to take the kids to watch the launch, they ended up having to reach out to an ISRO scientist and use a personal connection to get access. Now we can do it via a website. The advantage is that this is building up the hype for ISRO and getting more people interested in space.

The Science Objectives of the mission are as follows:

• 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 .

Full details of the mission are available at the ISRO: ADITYA-L1 Website. Will write more after the launch.

– Suramya