I just recently started working on my senior capstone design project for my aerospace engineering degree and am having to read up on the requirements and procedures for utilizing the DSN. BTW Scott Manley, your videos played a major role in me attaining this degree. 10-11 years ago I was a 20 year old automotive mechanic, I had a pretty sweet gig working for a company that trained race car drivers, so I spent my days building and maintaining race cars, worked on a couple of race teams as well. I had bought into the original KSP project back in the early early alpha days and my little laptop couldn't run it. But I had recently bought a new one and wanted to get into it and stumbled across your videos, your tutorials got me my first Mun landing and I was hooked. It was your Interstellar series that really got me going though. Your mix of educational exposition on the science and engineering concepts behind a lot of the gameplay in KSP sparked a passion and obsession with rocketry and physics that I didn't know I had. I soon found my self watching videos on theoretical physics and engineering concepts that were way over my head but fascinating nonetheless. Finally roughly 6 years ago I made the decision to quit my job as a mechanic and go back to school. I worked part time and took classes at the local community college for a couple of years. Then with the full support of my absolutely incredible family I made the transition into a full time aerospace engineering program at a large university. I'm now 32 and will be graduating in May with my aerospace engineering degree with plans to attend grad school afterwards. My dream is to one day work on next generation high-energy electro dynamic propulsion systems for powering interplanetary tugs. I may be a bit behind my peers in age but it's never to late to start learning new things. So thank you, without your content I don't know if I ever would have started this journey. Anyways, radio communication is some seriously like black voodoo magic stuff, the fact we are able to reliably transmit and receive data in environments with just miniscule signal to noise ratios using nothing but some linear algebra "trickery" is incredible.

@dianarising7703

Жыл бұрын

What incredible accomplishments! I hope you love your career.

@Theoryofcatsndogs

Жыл бұрын

good luck on your future journey!

@thomashiggins9320

Жыл бұрын

This is a great post. 😀

@paulloveless9180

Жыл бұрын

There are 3 one hour long documentaries filmed with radio nerds interviewing the actual NASA radio engineers. They go into incredible detail into every infrastructure complex including antenna structure, tuning procedures, amplifier strategies and much much more.

@kamakaziozzie3038

Жыл бұрын

Never too late to further your education! My wife who was an RN just finished her Phd in Biomedical engineering at age 55. Life is a journey.

As far as the Canberra site goes, it was originally at Honeysuckle Creek, which is the station that received "one small step for a man". (Despite what the movie "The Dish" may tell you.) It was decommissioned in 1981, being replaced by CDSCC at Tidbinbilla, down the hill from Honeysuckle, and somewhat closer to Canberra.

@stankythecat6735

Жыл бұрын

Tidbimbilla is so cool ! The dishes there are amazing

@ns219000

Жыл бұрын

‘The Dish’, despite being highly dramatized/fictionalized, is a really cool movie.

@TheBunzinator

Жыл бұрын

@@ns219000 Yeah, I enjoyed it. However, I know people who believed that the Parkes radio telescope was used for the Apollo 11 landing rather than DSS-44, because of that movie.

@neil2402

Жыл бұрын

No, Tidbinbilla did not replace Honeysuckle. In fact it opened 2 years before Honeysuckle! Tidbinbilla was for deep space, Honeysuckle was for manned missions (Moon, skylab, shuttle) and Orroral was for earth orbit satellite tracking. After Apollo/Skylab finished, Honeysuckle helped with DSN operations until it closed in 1981 and DSS44 was moved to Tidbinbilla.

@twelfthmanau

Жыл бұрын

I came to comments section for someone mentioning the Dish! Such a good movie!

Your video brings back many memories. By dad worked at Goldstone (and had a office at JPL as well) for over 30 years and ended up head of R&D for the DSN at Goldstone and was one of the founding fathers of VLBI until his death in 2011. Still remember when I was a kid spending a nights helping load, unload and labeling reel to reel computer tapes for experiments at Goldstone and Owens Valley telescopes and the Project Aries portable (kinda portable anyway, took 3 trucks to haul it) radio telescope during the early days of VLBI. Each tape held maybe 10 minutes of data and had 3 machines running. It seemed like we went through 100's of tapes a night but can't remember, I was 10 year old slave labor ;) It's amazing how the technology has changed over the years of the DSN. I moved out of state but when out in Cali visiting I always had to go to his office for a day to satisfy the geek in me and saw the progression of the DSN over the time of 25 years I can remember. Our 1976 Honda Civic had the vanity plate "VLBI".

That hybrid radio-optical dish plan was one of the few things new to me, but gosh that’s an exciting development!

Appreciate this excellent summary. Hats off to all the engineers over the decades for their hard work.

I went to visit the facility in Madrid. It is cool because it is in the middle of a cow pasture. They have a little visitor center and gift shop. I was shocked how many of my Spanish coworkers hadn't even heard of the facility. Great video.

@geirmyrvagnes8718

Жыл бұрын

I wondered if visiting was possible. Thanks!

@johnc2438

Жыл бұрын

...and you would probably be even more shocked at how many Americans -- or Southern California residents -- know nothing about the Goldstone facility or anything at all about the Deep Space Network. Those who are introduced have sometimes asked me, "Why spend this money on Space when we have so many problems in this country?" I worked at JPL for many years and grew tired of trying to explain that if we first solved "all our problems" (an endless, ever-evolving list), we would never have a space program. Of course, these people are full of opinions but are running on empty when it comes to knowledge. "It's a demon-haunted world" (apologies to Carl Sagan).

@cabc74

Жыл бұрын

I also visited it back in 2017. Those dishes are reaaaaallllyyyyy big.

I discovered the DSN website a few years ago, and was really blown away by all of the legacy and modern spacecraft that they communicate with.

Wow, the dish construction time lapse was amazing!

A week or two ago I actually rewatched the PBS Nova episode "To Boldly Go..." summarizing the Voyager missions, and it talked about how after Voyager 2's high-gain antenna died, they kept improving the DSN, enlarging the dishes and integrating dishes around the world into a single radio antenna array, during the years between planetary visits that were further and further from Earth. They also repurposed Voyager 2's third (spare) computer to perform image-compression computations, or else they wouldn't have been able to send back as many pictures as they did because of the dwindling bandwidth available.

I work at a place that just became the first DSN node outside of the three major complexes! The Space Science Center in Morehead, Kentucky, USA is now operating DSS-17 (a 21 meter X-band and S-band dish) as of a few months ago. I don't know why we don't show up on that NASA website. I got to move the dish one time, which was super fun.

@jtoscat

Жыл бұрын

I was scrolling through the comments wondering if anyone would bring up DSS-17!! I worked with Jeff Kruth, Tim Pham et al to build and implement the over the air end-to-end test setup (the little horn and LNA gingerly aimed in the MOC window). Hope the big gal is still running well!!

@stargazer7644

Жыл бұрын

It isn't listed because it is an "affiliated node", not an actual DSN owned antenna. There are quite a few antennas that help out the DSN network from time to time, but aren't DSN antennas.

JPLers call the control center for the DSN the center of the universe because basically most (deep space) spacecraft route all their communications through that room. If you ever get the opportunity to visit JPL and go the the SFOF viewing gallery, there is a JPL plaque in the floor of the darkroom (next to the Curiosity ACE console) and underneath it reads "The Center of the Universe 'dare mighty things'" If your escort can arrange a hosted tour by Jim McClure I'd highly recommend it too! He explains the reference better than I ever could. You also get to go into the Multi-Mission Support Area which is super awesome. (And you get to have some peanuts)

@rablackauthor

Жыл бұрын

You also get to see the cool light sculpture that flashes according to the signals coming in and going out. It's seen briefly at the 1:27 mark here.

@NuggetNapper

Жыл бұрын

@@rablackauthor Oh yes. It's called Pulse. Very mesmerizing to look at. There's also a counter of exoplanets around the corner from it. (And a neat exhibit on GRACE-FO)

Hey Scott, would love to see a video explaining more about how data is transmitted through space, compression, error correction, etc. Kinda similar to your recent video about air traffic telemetry. Really fascinating stuff!

@fredinit

Жыл бұрын

Watch CuriousMarc's series on Apollo Coms. He goes into some fairly deep dives on how they encoded voice, data, and video, along with ranging info.

@kid_missive

Жыл бұрын

Several presenters on Computerphile have comprehensive material on parity / error correction in excellent quality. It's not space comms specific but much of the tech is universal.

You're absolutely correct about the original DSN facility in Australia near Woomera, it was located nearby at Island Lagoon, called DSS41, and is definitely no longer in operation - completely dismantled. I travelled there a few years ago and all I could find was the foundations of the collimator tower, and a few curious red kangaroos quietly keeping an eye on us. In our travels this year, we wanted to visit it's modern counterpart at Tidbinbilla near Canberra, but the facility was closed due to COVID staffing restrictions, which was a shame. Instead we went north to CSIRO's Parkes radio astronomy facility, and that was pretty interesting, suitably satisfying my tech-geek appetite. Fantastic videos, choc full of good info... keep 'em coming!

I was fortunate enough to be stationed at Ft. Irwin in southern Cali. Just inside it's main entrance is the Goldstone Deep Space Complex and it's antenna dishes are scattered throughout the base. Because it's so far into the desert, at night you can clearly see both the Milky Way and easily spot the many lower satellites orbiting. That's where I bought my first Telescope and have been into Astronomy ever since. Thanks Scott!

The engineers working on the stations locally are quite active on Twitter, which is such a nice insight if you are interested in s specific topic. I have also seen them work together with amateur radio observers to get some neat signals decoded

Great video man! Always wondered about this

Just, Wow!! Love your work, Scott, but your light storytelling about the history of the storied NASA DSN is just incredible and makes this one of your best efforts ever!! Will be referring this video to science kids forever!! You have to get together with NatGeo, Smithsonian, or somebody like that to narrate a long-form documentary about this incredible subject!! We need you to become the David Attenborough of Astronomy and Space Science!!

EXCELLENT video, Scott! Thank you so much for that!

Amazing summary - thanks!

*_Great_** video, Scott...👍*

Great Video Scott! As being "Ground Station Guy" myself, I very appreciate giving the credit to ground comms for apace missions.

Thanks for all that information. I visited the Deep Space tracking station at Tidbinbilla, outside Canberra, a few years ago. You could see which probes were being communicated with, but your info was a nice addition. My 30 year old friend knew almost nothing about the moon landings, which featured in a display there.

Got to visit the Goldstone site when I was a JPL intern in 2015. Had to be one of the more eye-opening experiences of my life

Great video Scott

Excellent episode sir x

Pretty cool video, nice to see it's not in "relic mode" like it feels like so much of the space program can be some times. I had forgotten about the DSN Now site: just went and looked, and it's talking to Voyager 1, DART, Osiris REX, JWST (a slow uplink, a slow downlink, and a fast downlink), and the Korean lunar probe, among others, at this particular moment.

Thank you - no idea and will now visit Goldstone next family trip to the area!

'The Dish' is a great Australian movie about the Canberra site during the Apollo 11 Mission. It's not entirely factual, but it's a good laugh.

@theharper1

Жыл бұрын

Actually it's about the Parkes radio telescope which is quite a long way from Canberra which was the biggest dish in Australia at the time, but yeah, it's a great film! 😉

I toured hartebeeshoek south Africa in mid 90s it was still actively used and they were planing upgrades not sure of current state. And I can't be sure if any work done there was involving nasa and deep space network

@markiangooley

Жыл бұрын

Apparently NASA still has them do contract work occasionally involving certain spacecraft, says the Wikipedia page, but they’re mostly radio astronomy now.

Well done on saying Canberra correctly

Hey Scott, given that we've mentioned Goldstone in this video, could you talk about the XMM-Newton? There's a really interesting story there about it losing comms with ESA, and them literally using full power on Goldstone to induce a current in the comms circuit microswitch to turn it back on

I apreciate your explanations of subject matter that not only have I not heard of but even if I had I would not have understood until now.

Interesting video, as usual. Any chance of a follow up that discusses how the Soviet Union handled communication with their deep space probes? Or the Chinese, for that matter.

@FrikInCasualMode

Жыл бұрын

Oh, yes! Soviet era communication ships were extremely interesting constructions. Though data might be harder to obtain, because their other main function was to service ballistic missile tests.

Great video! I didn't realize how much science the DSN could conduct. I'll be rewatching this one soon! Love your stuff, Scott!!

That time lapse of the dish going up at the end was awesome. I've never seen that, probably because it doesn't happen often (or at all, where I live). 👍

Great video as always Scott! I have always been fascinated by the DSN

Super Cool Stuff! Thanks!😁😁

This is sooo neat. Lovely. i'm very happy about everything on astronomy.

Wow this was really interesting, thanks!

Super interesting video... A lot of new knowledge to digest 🤔 Think I might watch it a couple of times....😅

Dam that was good, had to watch this again Thank you

Thanks....what a great presentation..!!!

One of the dishes at Tidbinbilla, was at Honeysuckle Creek, where is was used to receive transmissions from Apollo 11, when the moon came over the horizon. Prior to this the transmissions were received at Parkes. There is very little left at Honeysuckle Creek, concrete slabs are all that remain.

Hi, Scott. Great video. I thought you might have pointed out that the positioning of a DSN in the southern hemisphere, Canberra makes it the only DSN component that can contact Voyager 2. As Voyager 2 is leaving us, below the plane of the orbits of the planets and is out of sight of the other two DSN locations.

Dude! Is there anything you don't know? You seem to have an intimate knowledge of the finest inner workings of all the stuff that you post. Thank you for sharing that knowledge with us! Much appreciated and enjoyed.

Thank you, Scott.

Absolutely fascinating

3:12 I really like how the DSN is able to bend radio waves around the circumference of the Earth like that! That's really COOL! :3

Nice time lapse at the end!

I have always wondered about this so thank you for the video. When younger I imagined 1970’s computers talking to older probes but later I realised it is just a matter of software to make it work. It would be interesting, though to take a look also into the intelligens part of the Deep Space Network.

I often hear about the DSN but rarely from it. Thanks.

That optic / radio dish is awesome

I got to tour the VLA in Socorro, New Mexico in 2010. At the time they were nearing completion of a major upgrade to the whole facility. The visitor center said that the total amount of data collected in the 40 years of operation up to that point was about two terabytes. After the upgrade was complete, they would be able to collect that much data every 100 seconds.

You don't quite realize how large these dishes are until you stand close to them and the operator turns the dish to dump out the snow on you 🙂 It wasn't the DSN since it was in Kiruna but it was the same size dish, mostly used to investigate the aurora.

Great video as always. As I worked on the Apollo Flight Journal over the years, I regularly came across references to the DSN, except that within Apollo, they referred to it (or at least a part of it) as the Manned Space Flight Network or MSFN. In the audio recordings from the time, it can be heard pronounced as 'misfin'.

I thought Jodrell Bank was part of the DSN. You learn something every day.

Thank you, Scott! This is a really informative episode.

It's nice to know SANSA (South African National Space Agency) and NASA starting a new deep space project in 2024. Looked up what the old project looked liked and came across it.

Interesting timing - was watching an amazing documentary about the Voyagers and how they triggered the need for the DSN. Genuine innovation.

Wasnt the University of Iowa North Liberty Radio Observatory part of the network? I remember setting it up for telemetry and data retrieval for early shuttle science experiments like the Plasma Diagnostic Package.

Scott Manley :- Fun fact. 4:40 I'm sitting in my room on a mine site, watching this video about 100km south of Woomera 🙂👌

Great rundown on the DSN, Scott. Thank you. Love hearing about the DSN Now website!

Good as always. I hope you can get some flying in today before the storm moves through tomorrow..

Fascinating!

4 receiving stations at the corners of a regular tetrahedron would be very satisfying - but if 3 is enough then it's enough.

Hi Scott!

Interesting post. It is easy to forget all the behind the scenes effort involved in these missions. I had not realized the DSN has a real time web page, cool.

Scott, this was very informative and I learned a lot about the Deep Space network. Which I first heard about in the 1960s.

Canberra's movie? No mention of Sam Neill and the sheep paddocks? Either way a great video summary. Ty!

If I recall correctly @eevblog has some Aussie DSN footage on his channel as well.

Developed all the radio just to go back to (admittedly souped up) flashing light. I can't wait until they realise the potential throughput of semaphore (maybe some kind of multi-colour pattern modulation for the laser comms) :p

Kind of cool that you caught DART and LICIA being tracked at the same time.

I remember reading about Venus' retrograde orbit as a kid, when it was discovered, but hadn't realized that the discovery was made using the DSN. Scott always delivers in his videos. Never disappoints.

Was Great in my cousin Vinny, judge Chamberlaind R.i.P Great actor 1993

Yes! The DSN is an underground celebrity that I ❤️

The Dish is such a fun, good movie. Give it a look!

Interesting that Tidbinbilla is now "Canberra". I wonder when that happened? Disappointed to not hear Mr Manley pronounce such a lovely word. :)

Truly magical space technology

Mindbogglingly interesting episode, Scott!!!! Well done!!!

Just one week ago I was so interested in the deep space network and low and behold you make the topic! What a miracle!

Mars Climate Observer's loss is commonly touted as a metric/Imperial units screwup, but it's really not. What actually happened was that the contractor provided the requisite thrust numbers without units. And the people at NASA entering the thrust numbers did it without first calling to confirm what the units were. They both assumed the other party was using the same units as them. If the numbers the contractor provided had been in kilonewtons, and the people entering them assumed they were newtons, the spacecraft would have been lost just the same even though all the units were metric. Important lesson for all you aspiring engineers and scientists: Except for dimensionless numbers, a number without a unit is as useless as no number. This was drilled into me in college - if I handed in a homework assignment or exam with the correct numbers but no units, I got zero credit.

So many of these machines are built using UNIX, or these days, Linux. It goes to show that if you build something good, people will use it. Proud of the amazing efforts by these engineers to share their knowledge with others to inspire them to become the next generation of scientists, engineers, designers, and, leaders of industry!

@TexanUSMC8089

Жыл бұрын

Linux is basically a GUI for Unix based systems. Kind of like windows is a GUI for DOS. I worked on many UNIX based servers.

@appleiphone69

Жыл бұрын

@@TexanUSMC8089 Linux is a kernel.

@Jump-n-smash

Жыл бұрын

@@TexanUSMC8089 Steve Ballmer would be proud of you, sir. Bloody good trolling.

@cabc74

Жыл бұрын

@@TexanUSMC8089 haha, you do not know much

The Muchea Tracking Station just north of Perth pre-dated Canberra by 5 years. It was set up in 1960 for NASA's Mercury program, it closed in 64.

Always a pleasure to watch your content

Synchronizing clocks using a pulsar blows my mind. Humans are insanely smart and capable!

where was final timelapse of building a dish filmed? and where can I see it?

That Pluto approach telemetry for New Horizons was the coolest fricken thing

I was soooo lucky to have a dad who worked his whole life at NASA/JPL and one time, while he was working in the group planning the trajectories for Voyager 1 & 2. Goldstone was way cooler than it was in the movies!!! Amazing what educated people can achieve when working towards the same goal. It was a long time ago, in the late 70’s

My father used to work at Goldstone running the telescope in the early 80's

I wonder if there was some kind of negative interation between the the deep space network station at woomera and JDF Nurrungar (the pine gap before pine gap).

thanks to your videos im passing my intro to space exploration course with flying colours!

Be really interesting to watch a video that talks more about how precise the measurements that are required to do Doppler-ranging out at Jupiter or Pluto and how accurately they can synchronise clocks at different sites for angular position. What sort of electronics were used in the past, and how does that compare to modern DSN kit?

@SeanBZA

Жыл бұрын

The modern way to get accurate time is a set of GPS locked hydrogen maser clocks at each location, so that the GPS signal, knowing your accurate location, and a long enough time, allows both atomic clocks to keep near perfect time with each other, and then you record the data with a time stamp and use a compute cluster to correlate the data to match each waveform to the corresponding one from the other. From that determine the delay due to distance, and solve the trigonometry. You have to sample at the carrier itself, which generates truly huge data sets, but you can use local computation to reduce the data volume, without sacrificing the time information, and once you have the data you can also average over a few minutes, to both get a motion vector compensation for the earth rotating, and also then the vector for the spacecraft moving. Before you would record both outputs using magnetic tape with an accurate clock, a Cesium atomic clock that was in a suitcase, that got flown there powered up, keeping the time from the master clock, and used to time stamp the data on the magnetic tapes. Then the tapes were flown back, and a room full of mathematicians solved the problem. Current methods rely on a high bandwidth link via the public Internet to do the backhaul in near real time, and NASA has the computer clusters to do the data handling as well in near real time as well, thanks to improving technology.

@nikkismith8750

Жыл бұрын

@@SeanBZA awesome! thank you so much :) Have you got any example numbers. eg, 10 femtosecond clock accuracy and 32-bit sampling the signal at 10GHz for 3 minutes gives 7TB of data to analyse for a precision of 100 meters at Pluto 6x10^12 meters? (obvs I have no idea - just pulled those out of thin air! lol)

@SeanBZA

Жыл бұрын

@@nikkismith8750 Not really, but you do get digitisers that will actually work at those bands directly, or with minimum downsampling. Enough bandwidth to get the data, and also the clocks are common these days for cellular towers, as they also use the accurate timing so as to coordinate all transmissions across an area.

When I play KSP, I usually create a "Deep Space Network" with large array functions. Usually one right at the outermost Kerbin orbit limit and then one or two in different orbits around the Sun - one closer to Eve and maybe another one closer to Duna or Jool. Thoughts on us doing this in real life soon as humans send more complicated, manned space craft further beyond just the Moon??

@nickdumas2495

Жыл бұрын

Also fun to do; spread a land based internet with probes on hills, and then have a tall tower at each pole (or spread around closer to the equator like DSN if you prefer) with the most powerful dishes to reach out to all the planets. Being ground based, their orbits never drift ;) The poles being perfectly flat came in handy when I needed to perch the actual transmitter vehicle on top of an independent tower vehicle so it counted as being higher above sea level for occlusion purposes.

Great video. This was so interesting. Computer and electronics improvements are incredible. Imagine they improved their data-handling by 10 to the 13th power.

Nice

if im ever near madrid i will defenetly try to go to see DSN

Scott, great presentation as usual. However, while I can't quote a source document, my understanding of the spacecraft impacting Mars is indeed a units error between Lockheed and JPL. Lockheed flew the craft up to the point just before orbit insertion, JPL took control beginning with the orbit insertion commands. There was not an error in understanding where the spacecraft was or how fast it was traveling. The problem was JPL thought the rocket thrust was measured in Newtons, but it was actually in pounds force. Therefore, when JPL commanded the insertion burn, it fired the thrusters 4.4 times longer than necessary - hence the spacecraft slowed too much and Mars definitely captured the spacecraft into a subterranean orbital altitude resulting in terra-braking instead of aerobraking.

@DrDeuteron

Жыл бұрын

it's called "Litho breaking". Terra is for earth. Mars is "Aeros" (e.g., its geoid is called "the aeroid"), so it sounds too much like air for braking. Anyway, I had heard there was a torque from radiation pressure on the space craft, which they corrected with thruster burns. I guess the torque part worked, but the thruster was interpreted incorrectly, and the S/C got off course. No one was sure what's up, and no one said, "let's check the units" (I always check the units)...so they did a TCM 4. (1,2,3 occur leaving earth, 4,5,6 are on the mars end), several engineers noticed a problem, and suggested a TCM5 fix, but upper managment nixed it. They watched it go behind mars and waited in vain for it to pop out the other side: crushing.

@scottyallen7237

Жыл бұрын

@@DrDeuteron Thanks for expanding my vocabulary, I appreciated learning some new terms. Lithosphere braking is indeed better descriptive jargon. However, since I did not capitalize terra, the meaning also refers to land or ground in general, not just Earth itself. In looking into failure reports of the Mars Climate Orbiter, the imbalanced solar pressure due to the asymmetrical solar array design did require many more momentum wheel desaturation burns than anticipated, possibly leading to the trajectory being closer to Mars than planned. However, there was a final orbit insertion burn, not just TCM burns, the commands for which were uploaded with values computed in English units. Since the spacecraft was too close to Mars, the insertion burn was likely 4.4 times too short instead of too long resulting in not enough altitude correction. Hence a combination of aerobraking and lithobraking to end the mission. In school, I had more than one math problem wrong because I had only the correct numerical value, but did not put the units with the answer.

scott manley intro be like *pt t pt t pt t a pt t a*

Great video Scott. But you have to be very careful... although I agree the DSN is AWESOME and truly an engineering marvel, the very talented engineers who design, build, and fly these amazing deep space explorers (Satellites) get very upset when you say the DSN "..Is the most important part..." LOL

Intriging how they diffentiate between incoming signals from different probes and program each with a separated band frequency modulation. Be amazing if an old probe that failed some how came back to life able to transmit data in one of the earlier configurations now obsolete? So every time they launch a new probe it has a new modulation in that band to distinguish it from another? Or the same modulation?