TYB
Hera asteroid mission’s CubeSat passengers signal home
28/10/2024
The two CubeSat passengers aboard ESA’s Hera mission for planetary defence have exchanged their first signals with Earth, confirming their nominal status.
The pair were switched on to check out all their systems, marking the first operation of ESA CubeSats in deep space.
“Each CubeSat was activated for about an hour in turn, in live sessions with the ground to perform commissioning – what we call ‘are you alive?’ and ‘stowed checkout’ tests,” explains ESA’s Hera CubeSats Engineer Franco Perez Lissi.
“The pair are currently stowed within their Deep Space Deployers, but we were able to activate every onboard system in turn, including their platform avionics, instruments and the inter-satellite links they will use to talk to Hera, as well as spinning up and down their reaction wheels which will be employed for attitude control.”
Launched on 7 October, Hera is ESA’s first planetary defence mission, headed to the first Solar System body to have had its orbit shifted by human action: the Dimorphos asteroid, which was impacted by NASA’s DART spacecraft in 2022.
Travelling with Hera are two shoebox-sized ‘CubeSats’ built up from standardised 10-cm boxes.
These miniature spacecraft will fly closer to the asteroid than their mothership, taking additional risks to acquire valuable bonus data.
Juventas, produced for ESA by GOMspace in Luxembourg will make the first radar probe within an asteroid. while Milani, produced for ESA by Tyvak International in Italy, will perform multispectral mineral prospecting.
The commissioning took place from ESA’s ESOC mission control centre in Darmstadt in Germany, linked in turn to ESEC, the European Space Security and Education Centre, at Redu in Belgium.
This site hosts Hera’s CubeSat Mission Operations Centre, from where the CubeSats will be overseen once they are flying freely in space.
Juventas was activated on 17 October, at 4 million km away from Earth, while Milani followed on 24 October, nearly twice as far at 7.9 million km away.
The distances involved meant the team had to put up with tense waits for signals to pass between Earth and deep space, involving a 32.6 second round-trip delay for Juventas and a 52 second round-trip delay for Milani.
“During this CubeSat commissioning, we have not only confirmed the CubeSat instruments and systems work as planned but also validated the entire ground command infrastructure,” explains Sylvain Lodiot, Hera Operations Manager.
“This involves a complex setup where data are received here at the Hera Missions Operations Centre at ESOC but telemetry also goes to the CMOC at Redu, overseen by a Spacebel team, passed in turn to the CubeSat Mission Control Centres of the respective companies, to be checked in real time.
Verification of this arrangement is good preparation for the free-flying operational phase once Hera reaches Dimorphos.”
Andrea Zanotti, Milani’s Lead Software Engineer at Tyvak, adds: “Milani didn’t experience any computer resets or out of limits currents or voltages, despite its deep space environment which involves increased exposure to cosmic rays. The same is true of Juventas.”
Camiel Plevier, Juventas’s Lead Software Engineer at GomSpace, notes: “More than a week after launch, with ‘fridge’ temperatures of around 5°C in the Deep Space Deployers, the batteries of both CubeSats maintained a proper high state of charge.
And it was nice to see how the checkout activity inside the CubeSats consistently warmed the temperature sensors throughout the CubeSats and the Deep Space Deployers.”
The CubeSats will stay within their Deployers until the mission reaches Dimorphos towards the end of 2026, when they will be deployed at very low velocity of just a few centimetres per second. Any faster and – in the ultra-low gravitational field of the Great Pyramid-sized asteroid – they might risk being lost in space.
Franco adds: “This commissioning is a significant achievement for ESA and our industrial partners, involving many different interfaces that all had to work as planned: all the centres on Earth, then also on the Hera side, including the dedicated Life Support Interface Boards that connects the main spacecraft with the Deployers and CubeSats.
“The concept that a spacecraft can work with smaller companion spacecraft aboard them has been successfully demonstrated, which is going to be followed by more missions in the future, starting with ESA’s Ramses mission for planetary defence and then the Comet Interceptor spacecraft.”
From this point, the CubeSats will be switched on every two months during Hera’s cruise phase, to undergo routine operations such as checkouts, battery conditioning and software updates.
https://www.esa.int/Space_Safety/Hera/Hera_asteroid_mission_s_CubeSat_passengers_signal_home
Kek.
I didn't have 1, 5 and 6, but I found a rare half year anniversary in my collection.
A Giant Structure in Space Challenges Our Understanding of The Universe
28 October 2024
A colossal structure in the distant Universe is defying our understanding of how the Universe evolved.
In light that has traveled for 6.9 billion years to reach us, astronomers have found a giant, almost perfect ring of galaxies, some 1.3 billion light-years in diameter. It doesn't match any known structure or formation mechanism.
The Big Ring, as the structure has been named, could mean that we need to amend the standard model of cosmology.
The discovery, led by astronomer Alexia Lopez of the University of Central Lancashire, was presented at the 243rd meeting of the American Astronomical Society in January, and has been published in the Journal of Cosmology and Astroparticle Physics.
It's the second giant structure discovered by Lopez and her colleagues. The first, called the Giant Arc, is actually in the same part of the sky, at the same distance away.
When the arc's discovery was announced in 2021, it puzzled astronomers. The Big Ring only deepens the mystery.
"Neither of these two ultra-large structures is easy to explain in our current understanding of the universe," Lopez said in January.
"And their ultra-large sizes, distinctive shapes, and cosmological proximity must surely be telling us something important – but what exactly?"
The most immediate link seems to be with something called a Baryon Acoustic Oscillation (BAO). These are giant, circular arrangements of galaxies found all throughout space.
They're actually spheres, the fossils of acoustic waves that propagated through the early Universe, and then froze when space became so diffuse acoustic waves could no longer travel.
The Big Ring is not a BAO. BAOs are all a fixed size of around 1 billion light-years in diameter. And thorough inspection of the Big Ring shows that it is more like a corkscrew shape that is aligned in such a way that it looks like a ring.
Which leaves the very unanswered question: What the heck is it? And what does it mean for the Cosmological Principle, which states that, in all directions, any given patch of space should look pretty much the same as all other patches of space?
"We expect matter to be evenly distributed everywhere in space when we view the universe on a large scale, so there should be no noticeable irregularities above a certain size," Lopez explained.
"Cosmologists calculate the current theoretical size limit of structures to be 1.2 billion light-years, yet both of these structures are much larger – the Giant Arc is almost three times bigger and the Big Ring's circumference is comparable to the Giant Arc's length."
But the size is just one of the problems. The other is what it means for cosmology, the study of the evolution of the Universe.
The current model is the one that currently fits the best with what we observe, but there are some features that are challenging to explain under its framework.
There are other models that have been put forward to address these features.
Under one such model, Roger Penrose's conformal cyclic cosmology, in which the Universe goes through endless Big Bang expansion cycles, ring structures are expected – although it's worth noting that conformal cyclic cosmology has significant problems of its own.
Another possibility is that the structures are a type of topological defect in the fabric of space-time known as cosmic strings.
These are thought to be like proton-wide wrinkles that emerged in the early Universe as space-time stretched, then froze into place.
We've not found much physical evidence of cosmic strings, but the theoretical evidence is pretty promising.
At the moment, nobody knows for sure what the Big Ring and the Giant Arc signify. They could just be chance arrangements of galaxies twirling across the sky, although the likelihood of that seems pretty small.
The best hope would be to find more such arrangements of galaxies, scattered throughout the Universe, hiding in plain sight.
"From current cosmological theories we didn't think structures on this scale were possible," Lopez said.
"We could expect maybe one exceedingly large structure in all our observable Universe. Yet, the Big Ring and the Giant Arc are two huge structures and are even cosmological neighbors, which is extraordinarily fascinating."
https://www.sciencealert.com/a-giant-structure-in-space-challenges-our-understanding-of-the-universe
https://iopscience.iop.org/article/10.1088/1475-7516/2024/07/055
https://www.youtube.com/watch?v=fwRJGaIcX6A