Rain in Paradise!

My first day back at QMC in 1981 after the Christmas/Hogmanay break was actually Friday 2nd January. Karen didn’t come in that day, but Carey, Nigel, Colin Spratling, and Brad Rose did. We had lunch together and, after work, Nigel and I went with Carey for dinner and then to the “Boy and Dolphin”, which was an excellent “spit and sawdust” pub. We then returned to Carey’s home for the rest of the evening. Good start to the new year.

During the next week or two I focussed on two sorts of work. One was designing, building, and testing various ultra-low-noise preamplifiers. The other was making the arrangements for my second trip to Hawai’i. The amplifier designs were aimed to kill two birds with one stone. They could be sold by QMC Instruments Ltd for various research applications, and a design was needed at that point to serve as the “moving coil” preamp stage for use in the Armstrong 700 amplifiers. The trip to Hawai’i was because John Beckman had been given time on UKIRT to use the mm-wave receivers systems we’d installed and commissioned during my first trip. I was going along to help run the receiver and ensure it worked correctly.

During my 1981 trip to Hawai’i I noticed some unusual cloud formations near to the Hale Pohaku base camp. In particular, one evening I spotted this ‘triple stack’ of lenticular clouds over a hilltop and they make a remarkable image!

Despite a lot of my work at QMC being on equipment for making astrophysical observations I wasn’t really ever an astronomer or astrophysicist. Yes, I did – and do – have an interest in astronomy, but my main interest always was engineering and being able to devise and build useful kit. That, in turn, enabled astronomers to make the observations they were after. For me, it was a very enjoyable side-effect that I then tended to end up finding I was getting to do interesting things like fly on Concorde or go up a volcano on Hawai’i!

One thing I noticed very quickly when I had joined the old ‘Astro Group’ at QMC and watched events over a few years was that lots of graduates wanted to be an ‘astronomer’. However the reality is that there aren’t that many day-jobs on offer that simply involve being an astronomer. So in practice, astronomy postgrads came and went like the tides. There always seemed to be a good supply of replacements. As a consequence, established research groups would tend to find it cheaper and easier to get a new one to do any donkey-work rather than find the higher amount of money to keep them on afterwards as a post-doc. However if someone developed key skills which helped enable established researchers to do their work, they were more likely to want to keep those skills handy. Hence in practice, a capable engineer was likely to find themselves a post-doc position because they had something to offer that was wanted which wasn’t available from a fresh-faced new post-grad student! This all suited me, because I have always liked to make things that others find useful.

At this point my initial post-doc position to develop systems for UKIRT was ending. So I was looking for other sources of employment as a post-doc. On Friday, 9th of January Keith Marries of QMC Instruments said he could let me have a lump sum payment for some consultancy work required by JET – the Joint European Torus project. This work was being organised via the NPL (National Physical Laboratory). It was the beginning of a series of bits of work I carried out for JET that continued even after I eventually moved from QMC to St Andrews University. The next day I flew from Gatwick to New York, then Los Angeles, and on to Hawai’i. I spent a night in the Holiday Inn at LA. Unlike what I’d expected, it was raining! On the Sunday 11th (local time) I went back to the LA airport for my flight to Hawai’i. What struck me at the time was that the people there seemed to behave in a much more chaotic way than I was used to at UK airports.

The people going on this trip were: Nigel Cronin, John Beckman, Marcus Chown, Robin Frost, and myself. Nigel and me were essentially the ‘technical bods’, going to help ensure the kit could be made to work and run the receiver. Marcus and Robin were John’s PhD students, and so the three of them were the astronomers. Marcus never did finish his PhD. Since that time he has commented to me that he seems to be a “serial PhD-dropper-outer”! I can understand this given that I didn’t write up a PhD, either, at the end of my original postgrad studentship. And of course, at this time I still didn’t have one, despite the work I’d been doing!

We had a long wait at LA. Nigel was arriving that day on a later flight than the one I’d taken. However although I’d been passed though Immigration and Customs easily, they held him up for over an hour. Despite this we caught our flight and arrived OK in Hilo, Hawai”i by 6pm (again, local time) on the Sunday.


Obligatory photo of me on a rock	Nigel, Robin, and Marcus at the hotel

John Beckman phoned the summit and they reported that the receiver had a high system noise temperature. They were also having problems locking the local oscillator to the required frequencies. This is not news which an astronomer would welcome because the system noise temperature is a measure how much (unwanted!) noise the receiver system itself is adding to what may be received. A high noise temperature will tend to ‘bury’ any wanted, weak, signals making them harder to detect or measure accurately. They also reported that they were, in practice, unable to observe anyway. This was because of very high wind speeds at the UKIRT site up on Mauna Kea. As a result, the UKIRT people were unwilling to open the dome because of the risk that the 80mph winds would damage the telescope or harm someone! The observers who had the telescope at the time were from Cambridge. This was their first night of the time allocated for their use, and hadn’t been able to do any observing at all. Our allocation wasn’t due to start until some days after our arrival. This was to give us a chance to acclimatise to the low air pressure, etc, at 14,000. We could use this period to visit the summit each day for increasingly long periods and get ourselves ready for the hard work once John’s telescope time began.

During our first night on Hawai’i we stayed at the Hilo Bay Hotel in Hilo, and it poured with rain there, as well! The rooms were cheap and noisy. Mixture of the sounds of deliveries to the kitchen and water pouring around outside – partly for a fountain, and partly the rain. We were tired enough not to be too bothered. However Nigel told me the next day that he was awoken at 4 am by his head being moved about on his pillow. This was the first, and most severe, of three earthquakes that night. Local news the next morning reported that its magnitude was 4·3 on the Richter scale and had a center at a depth of about 30 km. It was felt all over the Big Island – i.e. the actual island of Hawai’i. I did wake up myself at 4am, but didn’t realise what had happened at the time. Too tired by the outward journey. So I only learned why the next morning.

We arrived at Hale Pohaku during the morning of the 12th. The weather there was mild and fairly calm with only a moderate breeze. John and Nigel were given rooms in one hut whilst Marcus, Robin, and myself were given rooms in another. Having dropped our bags we went up to the summit for a brief visit. UKIRT was on an equatorial mounting. This means it was supported by two pillars - ‘north’ and ‘south’ – in a way that allowed it to rotate about an axis parallel to the Earth’s axis of rotation. Rather than being engineered to be rigid enough to survive an earthquake without damage the two pillars stood on flat plates, and were located with brass pins. These pins were designed to shear in the event of an earthquake, allowing the telescope to then take a walk rather than break. The first earthquake during the night had sheared the pins and shifted the telescope. Kent Susani (UKIRT staff) had moved the telescope back and inserted new brass pins, then started to check and tweak the precise telescope alignment. This was necessary for users to be able to point it accurately at the astronomical sources they would wish to observe. Alf (UKIRT technician) had gone up from Hale Pokahu on his way to the summit before we’d arrived. Having dropped off our bags we followed him.

This photo gives a better idea of what Robin looked like in those days. Note the trousers which give a clue that the 1970’s had only just ended! The photo also illustrates what the ‘dirt road’ and Bronco looked like.

One of the conditions imposed when permission was given to build the observatory was that no permanent paved roadway would be built to the summit. Instead, a ‘scraper’ vehicle was used to scrape a flat surface trackway for vehicles. Because of the weather and earthquakes this had to be regularly re-scraped to maintain its useability as a road.

As we drove up at about 11:30 there was yet another earthquake. We didn’t noticed this because we were in a Bronco (essentially a US vehicle similar to a UK Range Rover) bouncing along the rough road to the summit. But it sheared the pins again. As a result there was some discussion to decide if fitting new pins and going though the pointing alignment should be delayed in case another quake wasted the effort. Regardless of the high winds that had been experienced at the summit, there wasn’t any snow on the ground and it was fairly dry. Although two workers passed us in the common room wearing dust masks, so I assume the wind had kicked a lot of dust into the air. Dave Beatty (UKIRT staff) said the road to the summit was in poor condition at the time. Possibly also due to the weather they’d been having. But as it was our first day at the summit we came down again after a short period.

On Tuesday morning after breakfast, at about 8am, Nigel and I climbed up one of the small peaks to the south of Hale Pohaku. Gave us a chance to have a look around and enjoy the views. Around 11 - 12 am we spent an hour or so at the summit and I rang home to let people know we’d got there OK. Marcus seemed fine but Robin – who has asthma – felt a bit giddy so we wondered if he’d need to be particularly careful. However I used to have asthma a lot when a young child, yet if anything I found that being at altitude felt more comfortable to breath than at sea level! We had another earthquake at about 6:30pm. This one was about 4·7 according to the University of Hawai’i. The Cambridge crew didn’t get any data again, mainly due to telescope pointing errors. A consequence of the earthquakes and the telescope not being completely re-aligned as yet. The latest earthquake had sheared the pins in the south pillar again. Alf had needed to make a new set before this, so now had to make some more. As a result we expected that Cambridge would have similar problems over the next 24 hours. In addition, the weather at the summit over the last night had been quite misty which would degrade seeing. Judging by the rate at which the lowest cloud layer was rising up the mountain during the day it looked set to be misty again that night!

During the Monday/Tuesday night Cambridge had tried running the receiver at 230 GHz. This should have given optimum performance because the klystron (local oscillator source) for this frequency was a good one, and the system was designed with 230 GHz in mind. The reason for this is that one of the most common molecules in space that mm-wave astronomers wished to observe was CO (Carbon Monoxide). This has spectral lines at 115, 230, 345, etc GHz and is ideal for mapping clouds of interstellar gas. So a lot of time had been devoted to ensuring the receiver worked well at 230 GHz. However they only got a system temperature for the receiver of 800 Kelvin, which was higher than it should have been. Indicating something wasn’t quite right. The klystron was powerful, so that ruled out a lack of local oscillator power being the reason for the high noise levels. After dinner at Hale Pohaku we walked about a mile up the road with Robin. He was a little bit puffed out by the walk, but not enough to bother him.

This photo gives some idea of what the weather was like down at beach-level at the times it was windy and wet at the summit. It was a lot worse at the summit!

On the morning on Wednesday 14th we went up to the summit and stayed a few hours. No problems with the altitude and we all seemed to be acclimatising fine. During the Tuesday/Wednesday night Cambridge got a receiver noise temperature level of around 3,000 Kelvin at one point, which is particularly poor. (Note that the higher this ‘noise temperature’ value, the more unwanted noise the receiver is adding onto the wanted signal, degrading observations.) Later on they got the noise down to about 1,100 Kelvin which is better, but not ideal. One klystron which should have been oscillating at 115 GHz was thought to be running at around 120 GHz. But we weren’t sure if this was an error in the way it was used or measured at the time. The weather at Hale Pohaku was fine, but still misty at the summit during the night. Because of all the problems Russel (now Rachel) Padman hadn’t been able to get satisfactory observations of any of the objects they wanted to obtain. The combination of the earthquakes, weather, and difficulties optimising receiver behaviour had conspired to mess about with the ability to gather good results.

The next few days continued a similar pattern of poor weather, etc. This ran over the end of the observing time allocated to the group from Cambridge and into the start of the time allocated to John Beckman. As a result, although were were able to run some tests on the system and tweak its behaviour we, also, didn’t initially get any useful data. Indeed, The wind speeds were so high that we weren’t permitted to even open the dome! Hence on the Friday (16th Jan) Nigel, Robin, and I abandoned trying to work and came down from the summit at about 11:30pm. John and Marcus stayed on, and the wind did drop for a short period. The dome was opened, but then closed again quite soon when the wind got worse again. We’d managed to get system noise temperatures around 1,000 Kelvins. Not great, but useable if we could open the dome!

On the Saturday, we went up to the summit at lunchtime. The receiver was OK, but the wind speed was around 90 mph. Nigel started to feel ill at one point and felt sick and shaky, so he was driven down to Hale Pohaku to recover. This illustrates the curiously fickle nature of acclimatisation to altitude. I was never anything like as fit as Nigel. Both of us played squash at the time. But for me this was a struggle and almost anyone except a total learner would easily thrash me and then look for someone better to play! Whereas he was quick and fit and had stamina. He also had experience as a pilot and loved to fly. Yet he got caught by feeling unwell due to the altitude when it didn’t bother me at all. My conclusion was that my body had got used to always my finding breathing difficult, so I’d become hardened to the effects of altitude by decades of not being fit! Well, for couch potatoes, its a nice theory, anyway...

Oh, and the water pump in the UKIRT dome had failed. That meant there was no water to drink or to make tea or coffee. So we came down to Hale Pohaku in the evening and had dinner. The wind still showed no signs of abating. The comment I made at the time in my diary was, “If this keeps up, I’ll learn to play pool!” The ‘common room / dining’ hut had a pool table which we could use. I never did twig the rules for pool. And in practice when there was a small earthquake the balls used to move about. So we would probably have needed to devise some special ‘earthquake rules’ anyway. Earthquakes could be classified on the basis that weak ones made the pool balls move, stronger ones made the pots and pans in the kitchen clatter!

The above photo shows a view of NASA’s IRTF (Infra-Red Telescope Facility) seen from a point near to the UKIRT dome. You can also see the next island in the Hawai’ian chain in the distance, to the left

During the night of 17th/18th, John and Marcus came down from the summit at about 2:40am because the wind was too strong to permit observing. By then we had noticed that the lock-loop which controlled the local oscillator frequency seemed to be picking up some kind of interference. This was a plausible explanation for the oddly high noise temperature levels which the receiver had been exhibiting in use. The question then was, where was this interference coming from and how to stop it? A few days earlier Helen Walker (Imperial College) and Adrian had said that they’d noticed a 150 MHz signal on the system coming from somewhere and showing up as noise sidebands when they monitored the lock loop’s behaviour. Unwanted components like this may reduce the efficiency of the reciever. It might also cause the receiver to behave as if its attention was being split into simultaneously sensing more than one input frequency. That might then ‘dilute’ the wanted response and replace it with noise coming in from these other frequencies. Whatever the specific cause or details, the unexpected behaviour was a sign of problems that might be reducing the performance of the receiver. So it was something that I felt needed investigation.

To make working more, erm, ‘interesting’, the mains power at the dome had started cutting out randomly for a few seconds. This did tend to upset the receiver and the equipment used to gather the data, etc. Just to add spice to the experience, we would get a severe static belt off the telescope if we touched it after no-one had done so for a while. The static discharge was so big you could see the spark and it made my hand tingle, and left a pain in my finger for quite a while afterwards. This was probably due to the high wind and very dry air. But we did discuss if we should draw straws for who should be next to touch the system on the telescope when something needed to be adjusted. Then followed by a spark accompanied by an ‘ouch!’ in the darkened dome as someone resolutely did their sacrificial duty.

By the way: Yes, we did darken the dome when observing at night. Lights being on wouldn’t have affected our actually being able to use the mm-wave receiver. But if we had left lights on with the dome open at night that would probably have interfered with other astronomers using other telescopes who were trying to make observations at visible or near-visible wavelengths. In addition, being in the dark was useful for allowing us to see the sky more clearly. That said, the low oxygen levels did affect eyesight so in practice the human eye can generally see fainter stars from, say, around 5,000 to 8,000 feet altitude than from 14,000 feet up. Whilst at UKIRT Nigel Cronin did once try taking a few breaths from one of the emergency oxygen breathing mask kits to discover if he could then see the stars more clearly. But the main result was that he got a talking-to by the UKIRT people for doing this. It was potentially dangerous, and if happened often risked the oxygen supply being depleted when it was urgently needed!

One side-effect of the way the high winds had stopped us observing was that I’d spent more time watching US TV than was good for my, already dubious, sanity. Watching it gave me the feeling that the Americans must be crazy to put up with what was broadcast! Ignoring the quality of the actual programmes, the adverts were annoyingly pushy and – to put it politely – lacked any elegance or style. One example that made me fall about with laughter was an advert for a cat-food called “Meow Mix”. The tagline being, “The only food cats ask for by name!” I couldn’t tell at the time if this was an American version of Monty Python humour or if their target audience simply had no sense of the absurd. Did the advertisers assume the cats were smarter than their owners?... Or was this like the old British joke about a definition alleged to be found in an American dictionary – “Irony: contains iron.”?

At 11 in the morning on the 18th I hitched a ride to the summit with one of the cooks. Came down again at 6 pm because the wind was still too strong to do any observing. John then phoned down at 11 pm to say the wind seemed to be dropping, so I went back up to the summit. I started running up the receiver system, but I found the local oscillator was reluctant to lock on the frequency specified by the control computer. In particular, it refused to lock on when the frequency was near to the centre of the scanned range. Although I didn’t realise it at the time this was another clue to a problem which had been affecting the receiver for some time.

During my first trip to UKIRT we’d commissioned two Receiver Systems – ingeniously called ‘System A’ and ‘System B’. These shared a lot of the same equipment, but differed in some key respects. System A was designed to make observations in the frequency region around 230 GHz, but System B was designed for use in the 345 GHz region.

The systems shared the main parts of their Local Oscillator (LO) arrangement, and the computer system used to control the instrument. The basic LO source was a klystron running at a frequency around 115 GHz. The exact frequency was measured and used to generate a feedback signal which could then in turn be used to automatically tweak the oscillator’s behaviour and ‘lock’ the output onto the desired frequency. To use this LO and its ‘lock loop’ with System A the output LO power was fed thought a doubler to generate 2 × 115 = 230 GHz. This then went via an optical diplexer into a Shottky diode based mixer designed and built by Nigel Cronin to detect the incoming astronomical signals from the telescope. However this arrangement could be converted into System B by replacing the doubler, diplexer, and Shottky mixer with a tripler, a semi-reflecting sheet, and an Indium Antimonide (InSb) mixer.

As the name indicates, the tripler was designed to output 3 × 115GHz, i.e. 345 GHz. The InSb mixer had the advantage that it was capable of very good performance at these high frequencies – significantly better than any Shottky diode available to us at that time. And it only needed a small amount of LO power. However it had some practical limitations. In use, the main drawback was that it needed to be cooled down to almost absolute zero. At normal room temperatures (even at the summit of Mauna Kea!) InSb behaves like a normal metal conductor and wouldn’t function as a mixer or detector. However cooled down to near absolute zero it becomes a bulk semiconductor with a nonlinear response to an applied voltage. This means it can then be used to make a mixer or detector. But to be used in this way it has to be put into a vacuum cryostat and cooled down. Glenn White of QMC had built up expertise in this and used his own system based on it. He had therefore supplied a suitable InSb ‘bulk mixer’ for System B. The InSb mixer was in a cryostat, cooled down by the use of liquid Helium. This meant that it was operated at temperatures around 4 Kelvin or lower.

The other snag was that although such InSb detectors would work as mixers at very high frequencies their effective bandwidth was relatively narrow. The System A Shottky mixer could work with signal and LO frequencies which differed by 4 GHz, and would produce a difference-signal output with a bandwidth of hundreds of MHz. This was then passed to a correlator to make symultaneous spectral measurements covering hundreds of MHz while the LO frequency was kept static at the required value. However, in stark contrast to this, the bandwidth of the InSb mixer’s output was only about 1 MHz! As a result, when using System B it was necessary to ‘scan’ the LO frequency and observe the spectrum of the signals coming from the telescope, section-by-section. Hence rather than keep the LO frequency fixed, it would be rapidly ‘stepped’ from one value to another, making a measurement at each frequency in turn to build up the resulting spectrum measurement.

Note that for the sake of example, here I’m using the values of 115, 230, and 345 GHz as examples. I’ve chosen these because they are the frequencies of the Carbon Monoxide lines observed in many interstellar clouds. In practice the choice of klystron frequency would depend on the spectral line the astronomers wished to observe. (And for System A the LO would have to also be offset by 4 GHz.) There were a set of klystrons available for use with the receivers, and the people making observations would select the one that best suited the frequency they wished to observe. Glenn White used to keep and carry a small wooden case with a handle that contained a set of his ‘favourite’ klystrons. Each one of them tweaked and optimised for a given spectral line. Given that each klystron cost thousands of pounds and only had a nominal lifetime of a few hundred hours of use, he used to treat these with great care! The right klystron was the (expensive and delicate) key to being able to observe a given spectral line.

The level of control required in use can be seen by a simple look at the numbers involved. The resolution of the spectra output by System B was nominally around 1 MHz, although it could be set to be narrower by using an appropriate filter. That means a fractional resolution of 1 MHz at 345 GHz or 0·00029% ! Thus in order to make accurate measurements with System B it was necessary to be able to quickly step and lock the klystron’s output frequency with a precision significantly better than 0·0002%. And do this quickly enough to avoid any other parameters from drifting, altering the results. Because of this and the high frequencies, etc, involved, the lock loop electronics had to be rather more complex and impressive than I’ve shown in the above illustration.

Unfortunately, on the 18th we didn’t get a chance to open the dome at all because the wind speeds remained high, reaching well over 100 mph at times. At one point Nigel and I were outside of the dome on the lee side and one of the shutters from a window on the windward side flew past us, It had been ripped off by the wind! I also saw a sign by the road ripped apart by the wind. In some ways the velocities I’m reporting may be misleading because the density of the air was lower than at sea level,. However despite that reducing the force of the wind to some extent, the effects were pretty dramatic. I can’t now recall which day it was, but I also remember seeing one of the parked Broncos being blown uphill some yards by a gust of wind, despite the steep slope and its brakes being on!

The primary mirror ‘bottom end’ of the CFHT (Canada France Hawai’i Telescope). CFHT was housed in the biggest dome building on the site at the time. It was something of a prestige project and – if I recall correctly – even had a special lift for visitors and VIPs!

During Monday 19th Jan the windspeeds fell to ‘only’ about 60 mph. During the day Nigel and I finally found the gremlin in the lock loop system for the local oscillator. This was due to a poor contact in socket for a plug in an interface box carrying the control signals. One line of a parallel set was going open circuit. For some reason this caused the system to set the frequency to an unstable value the loop couldn’t hold. Afterwards I came to suspect that the ‘loop gain’ was also too high. I’ve seen other cases where this causes instability in some circumstances, and could also explain the earlier report of seeing 150 MHz ‘interference’ on the system. By 4:30 in the afternoon John had gone down to Hale Pohaku. The wind speed was rising again, gusting to 90 mph. At one point when the wind wasn’t too bad I was able to take a walk around the summit. But we gave up and started off towards Hale Pohaku at about 8 pm.

On the way down the Bronco Nigel was driving blew the rear right tyre. (Me, Marcus, and Robin as passengers.) When we stopped and looked, only the rim remained. We changed the tyre only to find the spare was flat. So we removed that and fitted the spare from Marc’s Bronco. It was, of course, dark. In the process someone who will initially remain nameless - but had been driving – managed to lose my torch. To end the day well, when we got to Hale Pohaku, Nigel, John, and I drank some whisky into the small hours with John Clarke, Bill Parker, and others. So although the day was a wipeout for observations it went well in terms of fixing the receiver and a convivial end.

I had initially intended to use the flights home from Hawai’i to the UK to either re-visit Kansas or some of the places in the USA I was interested in seeing. However by then I’d pretty well decided that I wouldn’t be emigrating to the USA. So I decided that after the telescope time allocation had finished I’d take a holiday in Hawai’i instead to relax and unwind. With this in mind I started phoning the airlines like Hawaiian Air, American, etc to decide what flights I’d book. One thought was to fly over to Kawai’i (one of the smaller islands in the chain) as a change from the Big Island.

On Tuesday morning Nigel revealed my torch with a flourish. He’d forgotten it was in his duvet (suit) pocket. Naturally, he’d left it switched on, so the batteries were now totally flat. Another round he owed me! Spent the afternoon and evening at the summit where the weather continued as before. Wind speeds around 80 mph. As we left the summit I noticed a lens-shaped cloud had formed over it which looked very similar to the cloud formations I’d seen over Mauna Loa during the previous few days. The cloud seemed almost static, but presumably was reforming itself in-situ as the wind carried the air over the peak. The observatory doctor took my blood pressure during the day as a check. This came out as 135/95, which is actually quite similar to when I measured it over 30 years later at sea level.

Me standing beside System B . The gold-coloured object near the end of the receiver system closest to me was the liquid helium cryostat/dewer which contained the InSb mixer/detector.

On Thursday 22nd January we took the receiver off UKIRT and moved it outside of the dome on a fork-lift truck to do some measurements of the atmospheric conditions. During the day I phoned ticket agents to arrange my flights. I also phoned Mary Jane Butler to let her know I’d decided not to visit Kansas on my way home. I said that the weather was bad and I was to stay on in Hawai’i to do atmospheric measurements. However we couldn’t actually make any observations because the summit was covered by freezing fog.

Unfortunately the cryostat used to keep the InSb detector cold had developed a slow air-leak. This reduced the quality of the vaccum, allowing excess heat into the dewer, and degrading performance. So during the day I took the dewer over to the IRTF (Infra Red Telescope Facility, financed by NASA). They had a leak detection system which could help me to locate where any leaks were. This let me find one leak in the surround of the ‘window’ which let mm-wave signals in to the detector. And another leak at the top of the dewer, beside where it was filled up with liquid Helium. Having fixed these leaks, John drove us down at the end of the day. Alarmingly, he lost control of the Bronco on one of the corners on the unpaved road. Then he, twice, got into a four-wheel skid on corners. He may have been tired or affected by the lack of air, but it was quite scary at the time!

The next day I took a break and stayed at Hale Pohaku whilst Nigel and John ran the receiver. They managed to get some sky dips to assess how the atmosphere’s transparency varied with vertical angle of the line of sight at 345 GHz. However when I looked at this it seemed to show that the wet air was actually flowing over the summit in a curved ‘dome’ shape rather than being horizontally stratified. Over the next few days we made a series of atmospheric measurements before finishing our work with the receiver systems and putting them back into the UKIRT dome.

What the coast of Hawai’i looked like when the weather was good!

On Monday 26th I was driven down the mountain. The driver was one of the cooks from Hale Pohaku and he drove like a madman! I was surprised to arrive in Hilo alive and well. We all stayed that night at the Hilo Bay Hotel and we got very drunk indeed. This wasn’t intended but happened for two reasons. Firstly, having come down to sea level after a number of days at altitude we felt amazingly alert and lively. Afterwards I realised we were already a bit ‘drunk’ because we were taking in so much more oxygen than during the last couple of weeks. The other was that we’d forgotten that spirit-based drinks in the local hotels and bars had a lot more alcohol per drink than the standard measures back in the UK! As a result after even just a few drinks we went up to bed and quickly then found we felt very drunk. As a result, in the morning I wanted to take it easy and have a quiet and relaxing day to recover again.

During the days after finishing work at UKIRT John and I went to various places around the Big Island to sightsee, etc. I also island-hopped to Kaua’i, which is a relatively small island at the other end of the chain, and toured around that for a day or two. A great deal of the land area on the Big Island is rocky and stark, clearly volcanic. However, Kaua’i is much more like what people in the UK might envisage in response to the phase “tropical island in the Pacific”! Lush green coverage and a warm damp environment. Quite beautiful. On Saturday 31st Jan I started the long process of flying back to the UK via Honolulu (O’ahu) and Los Angeles. Arrived back home in sunny Forest Gate in London on the 2nd of February after lunchtime. Didn’t sleep for 24 hours during the journey and at that point at 4pm London time my body thought it was 6am Hawai’i time! But I managed to watch a TV episode of the “Hitchhiker’s Guide to the Galaxy” that evening before getting some sleep. That said, I preferred the radio broadcast version!


IRTF	CFHT building


River views on Kaua’i.