After the fire and fury of liftoff, when a spacecraft is sailing silently through space, you could be forgiven for thinking the hard part of the mission is over. After all, riding what’s essentially a domesticated explosion up and out of Earth’s gravity well very nearly pushes physics and current material science to the breaking point.
But in reality, getting into space is just the first on a long list of nearly impossible things that need to go right for a successful mission. While scientific experiments performed aboard the International Space Station and other crewed vehicles have the benefit of human supervision, the vast majority of satellites, probes, and rovers must be able to operate in total isolation. With nobody nearby to flick the power switch off and on again, such craft need to be designed with multiple layers of redundant systems and safe modes if they’re to have any hope of surviving even the most mundane system failure.
That said, nobody can predict the future. Despite the best efforts of everyone involved, there will always be edge cases or abnormal scenarios that don’t get accounted for. With proper planning and a pinch of luck, the majority of missions are able to skirt these scenarios and complete their missions without serious incident.
Unfortunately, Lunar Trailblazer isn’t one of those missions. Things started well enough — the February 26th launch of the SpaceX Falcon 9 went perfectly, and the rocket’s second stage gave the vehicle the push it needed to reach the Moon. The small 210 kg (460 lb) lunar probe then separated from the booster and transmitted an initial status message that was received by the Caltech mission controllers in Pasadena, California which indicated it was free-flying and powering up its systems.
But since then, nothing has gone to plan.
Spotty Communications
According to NASA’s blog for Lunar Trailblazer, Caltech first heard from the spacecraft about 12 minutes after it separated from the second stage of the Falcon 9. At this point the spacecraft was at an altitude of approximately 1,800 kilometers (1118 miles) and had been accelerated by the booster to a velocity of more than 33,000 km/h (20,500 mph). The craft was now committed to a course that would take it away from Earth, although further course correction maneuvers would be required to put it into its intended orbit around the Moon.
The team on the ground started to receive the expected engineering telemetry data from the vehicle, but noted that there were some signals that indicated intermittent issues with the power supply. Around ten hours later, the Lunar Trailblazer spacecraft went completely silent for a short period of time before reactivating its transmitter.
At this point, it was obvious that something was wrong, and ground controllers started requesting more diagnostic information from the spacecraft to try and determine what was going on. But communication with the craft remained unreliable, at best. Even with access to NASA’s powerful Deep Space Network, the controllers could not maintain consistent contact with the vehicle.
Tumbling and Off-Course
On March 2nd, ground-based radars were able to get a lock on Lunar Trailblazer. The good news was that the radar data confirmed that the spacecraft was still intact. The bad news is that the team at Caltech now had a pretty good idea as to why they were only getting sporadic communications from the vehicle — it was spinning in space.
This might not seem like a problem at first, indeed some spacecraft use a slight spin to help keep them stabilized. But in the case of Lunar Trailblazer, it meant the vehicle’s solar arrays were not properly orientated in relation to the sun. The occasional glimpses of sunlight the panels would get as the craft tumbled explained the sporadic nature of its transmissions, as sometimes it would collect just enough power to chirp out a signal before going dead again.
But there was a now a new dimension to the problem. By March 4th, the the spacecraft was supposed to have made the first of several trajectory correction maneuvers (TCMs) to refine its course towards the Moon. As those TCMs never happened, Lunar Trailblazer was now off-course, and getting farther away from its intended trajectory every day.
By now, ground controllers knew it was unlikely that Lunar Trailblazer would be able to complete all of the mission’s science goals. Even if they could reestablish communication, the vehicle wasn’t where it was supposed to be. While it was still theoretically possible to compute a new course and bring the vehicle into lunar orbit, it wouldn’t be the one that the mission’s parameters called for.
A Data-Driven Recovery Attempt
The mission was in a bad place, but the controllers at Caltech still had a few things going in their favor. For one, they knew exactly what was keeping them from communicating with the spacecraft. Thanks to the ongoing radar observations, they also had highly-accurate data on the velocity, position, and rotation rate of the craft. Essentially, they knew what all the variables were, they just needed to figure out the equation that would provide them with a solution.
Over the next couple of months, the data from the radar observations was fed into a computer model that allowed ground controllers to estimate how much sunlight would hit Lunar Trailblazer’s solar array at a given time. Engineers worked with a replica of the spacecraft’s hardware to better understand not only how it operated while in a low-power state, but how it would respond when it got a sudden jolt of power.
The goal was to find out exactly how long it would take for the spacecraft to come back to a workable state when the solar array was lit, and then use the model to find when the vehicle and the sun would align for long enough to make it happen.
It was originally believed that they only had until June for this celestial alignment to work in their favor, but refined data allowed NASA and Caltech to extend that timetable into the middle of July. With that revised deadline fast approaching, we’re eager to hear an update from the space agency about the fate of this particularly tenacious lunar probe.
Should have used silver-zinc batteries (charged by solar panels).
They apparaently had worked reliable some 65 years ago.
https://en.wikipedia.org/wiki/Venera_1
https://en.wikipedia.org/wiki/Silver_zinc_battery
Those things are very heavy.
The problem isn’t the solar panels or the batteries.
The problem is that the probe is (or was) tumbling. It is spinning in a way that it wasn’t intended to do so that the solar panels don’t get enough light to charge the batteries.
Silver-zinc was the highest performance battery technology before lithium batteries were developed. Lithium batteries outperform silver-zinc batteries. It is doubtful that a silver-zinc battery would have lasted the planned two year Lunar Trailblazer mission.
” Lithium batteries outperform silver-zinc batteries”
*Did. The Wiki page says otherwise.
“Experimental new silver–zinc technology (different to silver-oxide) may provide up to 40% more run time than lithium-ion batteries and also features a water-based chemistry that is free from the thermal runaway and flammability problems that have plagued the lithium-ion alternatives.[1]”
https://en.wikipedia.org/wiki/Silver_zinc_battery#Overview
While experimental tech may prove to be a better option, the “may” in that sentence is really the most important part right now. It’s not here yet, and like many experimental technologies, it may never materialize.
Something better will come along eventually, and it’s good that people are trying lots of options, but don’t count your chickens before they hatch.
“The problem isn’t the solar panels or the batteries.”
Not directly, but indirectly it is.
“The problem is that the probe is (or was) tumbling.
It is spinning in a way that it wasn’t intended to do so that the solar panels don’t get enough light to charge the batteries.”
That’s the usual problem of insufficient main power/auxilary power.
An RTG or high-capacity backup battery should at least keep the command unit/receiver going – for multiple days or weeks.
Exactly for such a situation. That beast weights over 200kg and doesn’t have the equivalent to a modern 12v 7A or 20A lead-gel battery?
An ordinary VHF two-way radio can run a couple of days with that (RX only).
The RTG idea is what came into my mind. Would one of sufficient size for the purpose of temporary “emergency” power add too much weight to the craft? Is it possible to (manually or automatically) turn it on when needed and off once issues with or affecting the primary power source (solar in this case) are resolved?
One does not simply turn off an RTG.
If loss of power due to loss of attitude control was a plausibly recoverable failure mode, it would have been cheap and easy to simply use bifacial solar panels, or panels covering several faces of the satellite.
Simply adding a bucketload of batteries “just in case” is a poor way to spend a mass budget.
Many satellites used to use solar cells on many surfaces, whether spin-stabilized or uncontrolled, or other reasons.
Many satellites (especially cubesats) still use the “spare panels” strategy. One I know of has panels on three faces that are not deployed to be sun-facing until attitude control is established, and then the fourth side remains in the dark. This satellite has a “sail” mode for orbit maneuvering that sometimes puts its primary panels in an unfavorable solar orientation, so the fourth panel also helps in that situation.
Yeah, the power is really exacerbating the problem, not really the fundamental cause. If you don’t have attitude control you don’t have a spacecraft, you’ve got smart space debris.
Please tell me how you know that, because I can’t find the spacecraft’s battery capacity anywhere public.
What I can find is that the solar array is specced at 280 W, which I would expect to be accompanied by a battery on the order of several hundred Wh to a kWh to provide adequate cycle life for several years in an eclipsing low lunar orbit.
That’s consistent with some other order-of-magnitude estimates that can be made about the power budget. You’d expect power consumption during payload operations to be around half, or a little over, of the solar array capacity, so let’s say 150 W. Guess that the majority of that is allocated to the payloads, leaving maybe 50 W for the computer, software-defined radio, and various accessories like star trackers and reaction wheels. For rad-hard components, running a decade or two behind the curve, that’s not shockingly high. And since it drained its battery in 10 hours after launch, that guess would align with a battery of several hundred watt-hours.
So yeah, a lunar spacecraft is probably a little more demanding than your Baofeng. Go figure.
“So yeah, a lunar spacecraft is probably a little more demanding than your Baofeng. Go figure.”
Sadly, yes. Meanwhile, there are Arduino Uno based CubeSats that can easily operate in the earth’s shadow.
And they also have transceivers, with everything running via a small, humble lithium battery pack.
At least for the control unit/receiver there should be a separate battery in such a space craft.
Because the worst that can happen is an space craft that goes on/off erratically and keeps occupying valuable frequency spectrum for years to come.
That’s why space agencies shouldn’t be cheap on backup batteries.
Accidents in space business are the norm, rather than the exception.
The modern “sunshine technology” they use is fragile and only works flawlessly under best condition (nice weather).
60 years old probes had batteries that lasted longer or so it seems.
Sputnik 1 ran for 3 months without any solar cell, for example. And it did transmit all the time. 3 months!
Thus, they should at least make sure a passive receiver is running all time, so the space craft can be shut down manually from earth.
Either temporarily or permanently (kill switch). IMHO.
.. and if they absolutely can’t afford a proper backup battery, then they should at least give such probes a crystal radio! And an Attiny 13 MCU!
It needs so little power that the crystal radio can power it, as well if needed! Sigh. 😮💨
“Meanwhile, there are Arduino Uno based CubeSats that can easily operate in the earth’s shadow.”
It’s amazing how much help you get from a planetary-scale magnetic field.
@Joshua: Nice weather? In space?
@Pat That is a reference to the bird’s electromagnets for attitude control?
I’ve rather meant the battery reserves for recurring power outages during the “night”.
In any case, using a crystal radio as an emergency receiver isn’t that far-fetched. ;)
Some MCUs can operate at very low power (microamp range).
By transmitting a few hundred watts via radio waves from ground control,
there should be at least a few milliamps available after it passes through the crystal detector.
This is enough to disable the satellite/sonde from a distance.
Confirmation from the probe is not required, the communication link could be unidirectional.
If it’s suddenly becoming quiet, it’s working. :D
For example, the communication could be similar to using “UI Frames” in APRS.
Might as well work without an MCU altogether.
A sequence of pulses of different lengths, etc.
A few 555 might be able to do that.
By the way, there was a time when satellites and probes were completely analog.
They sent back telemetry data with multiple modulation types, such as FM.
The coding was done using different time slices etc.
@Chris Maple “space weather” :D
“This is enough to disable the satellite/sonde from a distance.”
The issue with adding redundancy and backup options is that it does not automatically increase reliability. If you add a power source for redundancy, you’ve just moved the single point of failure from “first power source” to “power transfer switch.” It’s still there. You’re talking about giving an MCU control over the entire spacecraft via a crystal radio. Great. Now you have to think about all the ways that can fail in a deep-space situation and determine if you’ve actually improved things.
Adding redundancy for a failure that likely results in total loss of the spacecraft anyway (again – the spacecraft here is tumbling, it was likely a goner from the beginning, they’re just trying to get something out of it) is not an improvement. It is only adding additional complexity and new failure points for the 90%+ of times the spacecraft doesn’t exit deployment in an uncontrolled tumble.
Going through the failure point analysis is common. One of the common questions is “what happens if there’s a launch/deployment failure into X situation” and in most of those situations the answer is “total loss,” and that’s fine. The best and cheapest mitigation for that if you’re really worried is “build two spacecraft” and in a lot of cases, they do (because two spacecraft doesn’t cost twice one). But it’s just a question of whether or not the science warrants it.
“An ordinary VHF two-way radio can run a couple of days with that (RX only).”
And do what? Listen to Earth and not be able to actually power anything or respond back?
As someone actively involved with stuff like this: spacecraft design is hard. The thermal design alone is a giant pain in the neck, nothing works the way it’s supposed to, and it’s a whole lot of “what the hell is going on” while staring at fragments of data received bit by bit.
“spacecraft design is hard.”
Yet same time, ordinary people, -laymen-, managed to build lasting satellites with relatively humble resources.
For a start, I recommend reading about the history of the ham radio satellites.
It’s kinda related to the history of the RCA 1802 processor, too.
That processor was very nifty, also because it could work with a large range of operating voltages.
And the amateur satellites didn’t even use the space-hardened version of the 1802.
If you have some extra time, I recommend reading about the AO-10/AO-13 sats and the IPS software.
Because, these sats had to overcome some issues, too.
Communication was established via AX.25 HDLC protocol.
Humble home computers such as Atari 400/800 had been used on ground, for example.
Two historical videos with footage of the sats can be seen here:
https://www.youtube.com/watch?v=zGan3WE8C64
https://www.youtube.com/watch?v=GDR4pqkmmxE
“history of the ham radio satellites.”
Low earth orbit versus deep space. Massively different. You can chuck smartphones into LEO and they’ll probably work.
Case in point:
https://www.spaceselfie.com/
“Low earth orbit versus deep space. Massively different.”
Maybe. At least AO-7 isn’t an average LEO satellite, though.
At a distance of 1000km, it’s at the outer limit of LEO.
It also very old and it went silent for a while during a battery damage.
It must be said that at the time, such sats didn’t necessarily have proper battery chargers yet.
They’ve utilized the fact that NiCD batteries of their time could be charged more or less directly from solar panels.
Which wasn’t as healthy for battery life as if using chargers, though.
https://www.theregister.com/2024/11/25/amsat_oscar_7_anniversary/
“You can chuck smartphones into LEO and they’ll probably work.”
What a surprise, I always thought it needs a C64.
I wonder if the smartphone sat still works after passing the south atlantic anomaly.
“At a distance of 1000km, it’s at the outer limit of LEO.”
That’s just a designation for orbit management. This is a deep space satellite. It’s just different.
As ever, I’m here to read all the experts in the comments section who know better than the rocket scientists.
I don’t see anyone claiming to know better. They are simply discussing ways in which the impact of the current issue could have been reduced.
The problem is that the designers rarely have any control over the final design. I’m sure I’m not alone here in having the work ‘red pencilled’ by some middle manager trying to make himself look good because, and I quote:
“We’re not wasting money on something that will probably never be used.”
“that the designers rarely have any control over the final design.”
I do this stuff for a living. This is just not accurate in the least. There are no “middle managers” red-penciling things on stuff like this. Cost-cuts on redundancy happen due to cost, power, development time, or mass/volume constraints.
“I do this stuff for a living.”
And?
I’ve heard that in the States a lot of unqualified people can do the jobs they want to do.
If I understand correctly, they can claim to be an electrician
and just start working as such without ever having been apprenticed for years to a master
and having received their master’s certificate. That’s wild!
Anyway, it just came to mind because this (?) an US centric site.
And?
Personally I love it when people applaud cheap NASA missions (it’s a sub-$100M lunar satellite that took like 5 years to develop including the pandemic, f’crying out loud!) when they succeed being like “see, how great is it we can do this!” and then promptly suggest eight billion add-ons that’d balloon the development time/cost/etc. when one of them fails.
They’re gonna fail. They’re gonna fail more often than the multi-billion dollar old satellites do. But there’s soooo much more of them that it just doesn’t matter.
Kek, my comment about a waste of $94.1 million in taxpayer funds was removed.
Somebody can’t handle facts
“Somebody can’t handle facts”
That’s rather ironic coming from someone who’s opposed to a space mission designed to gather ‘facts’
Please explain exactly what new “facts” will be uncovered by a broken satellite that probably won’t be recovered.
Hell please explain what NEW facts it would gather if it were working correctly. Its was supposed to look for water on the moon. Yeah we haven’t ever done that before. Eyeroll.
Simulation software was written, valuable experience was gained by the engineers, and if they manage to make it work: they will have turned a failure into a success.
It’s an expensive lesson. But a lesson nonetheless. Never try, never win.
Besides, $94 million is peanuts compared to the $4,900,000 million in tax money that the US collects every year. 0.0019% of tax payer’s money ‘wasted’.
I’m sure that the government wastes more tax payers money on damage caused by citizens. Yes, I’m calling that a waste, because those citizens never learn and will keep damaging public property whatever the government does to educate them. Billions of dollars go to waste there, which never change facts, ever.
Plus the tools, design, operational software, etc. all exist, and there’s likely additional flight hardware that could be repurposed into a second craft for significantly less. If you actually price out just the physical spacecraft itself it’s likely quite a bit less than that.
It’s more than you’d think because you basically buy a commercial “delivery vehicle” (so that’d need to be bought again) but failed missions very often end up with second lives on other spacecraft.
It’s common for people to treat these things like “products” or “companies” but synergy between projects and reuse are specifically called out and valued in proposals.
I agree with everything you said. I don’t care how little the waste is though when the National debt is rapidly approaching the point of no return and US credit has already been downgraded a couple times.
A mission to do something that has already been done and will yield no tangible benefits is waste.
It’s macroeconomics. Countries aren’t people or businesses. You don’t actually save money on something if cutting it hurts your economy in future years. It’s the same reason why states offering in-state scholarships to top students who agree to stay in state after they graduate is smart.
What’s driving the deficit in the US isn’t discretionary spending, it’s nondiscretionary. You need to fix that, not kill stuff that ends up netting positive money in the longer term. It’s like cutting food out of your budget and then being shocked when you lose money due to the hospital visit cost after you pass out.
Where exactly do you think all the people who are leaving the sciences due to funding being cut are going? You think they’re staying in the US and getting factory jobs or something? They’re going overseas – they’re being invited overseas, which means now you’re going to have more tech development and research occuring there and not here. Not to mention the national security issues. These are rocket scientists we’re talking about.
If you want to point to economics studies that say that investing money in science like this is a waste, I’d agree with you. Except – oh wait, there are buckets that say the exact opposite.
NASA again ‘eh?