Related posts:

1. Train from Mumbai to Pune

Naturally, the control room is the same as before. But I neglected to show what I actually look at when I am “monitoring” the observations. An important part of observing is making sure you are actually getting useful information, and not wasting the telescope time. When optical observing this usually means doing simple calibrations of the images (or spectra) you are taking and comparing it to your expectations based on the rough capabilities of the telescope. (It’s almost important to make sure your telescope is pointed at the right object!). When observing with a single-dish radio telescope you are combining the spectra to look at the amount of energy emitted by an object at a given wavelength. Again, you are checking the quality of the data to be sure the systems are functioning normally.

Arrays of radio dishes combined into a single array are monitored a bit differently. Instead of doing a quick calibration of the data and checking the result (as done frequently in many optical and single-dish radio observations), the raw data products are easier to monitor. This is due to the fact that making images from an array is computationally intensive and somewhat time consuming. The time consuming portion can be alleviated by running the data through a pipeline, but it can still take some time to arrive at a “raw” data product suitable for monitoring the observation. In other words, it can take so long to get the “first look” data that it is too late to fix your observation.

These arrays work by comparing the signal recorded from pairs of dishes. So, you can monitor the health of the antennas by looking at these pairs of antennas. Below is a screen capture of a plot I viewed to monitor the status of the observation. The plot shows the amplitude (strength) of the signal against time (IST is Indian Standard Time). This amplitude is measured by comparing the signals received between two telescopes.

The key to each plot tells you what data you are looking at. For example: “W03 – USB 130:C09″ denotes the amplitude measured by the antenna pair W03 and C09 (an antenna on the Western arm of the array and an antenna in the core of the array). For this plot, I am only showing amplitudes on baselines with C09. Can you tell which antennas aren’t working properly? (Hint: they are reporting very low amplitudes.)

Antennas S04 and C01 both appear to have issues, based on the low amplitude of the signals.

There is also a range of amplitudes in the signals from the other antennas paired with C09. The highest amplitude values (at the beginning) are observations of the flux calibrator (for descriptions of the calibrators, see this post). The next highest values are observations of the phase calibrator. Finally, the values that are nearly zero at this scale are observations of the science target. The amplitudes are lower because the science target is over 100x fainter than the flux calibrator.

This is of course only one way to monitor observations. You can also look at the phase, because light is a wave. The phase contains information about the structure of the source, but rapid variations of phase with time are signs of a problem.

These plots are updated as more data is taken, so monitoring these throughout the observing run can allow you to detect some potential problems with the observation. Naturally, you can’t catch everything. But, the big problems will usually be visible. Once the observation is concluded, the more subtle issues can usually be resolved.

Related posts:

1. Live from the Giant Metrewave Radio Telescope
2. More 1.4 GHz Observing
3. 10 Hours into the Observing Run

As I drove back from the GMRT on Monday evening, there was a very nice sunset. As was passed through the outskirts of a town a flock of birds took to the skies and flew parallel to the road for a bit, silhouetting themselves against the sunset.

Related posts:

1. No storm, but we had a sunset
2. Sunset on Lake Reynovia
3. Sunset on the Heath

Right now I am 5.5 hours into a 9 hour observing run at the Giant Metrewave Radio Telescope near Pune, India. I am observing neutral hydrogen in other galaxies as part of my PhD thesis. We had a bit of a hiccup at the start, getting some parameters set so we were observing the right frequency. But that got sorted out and we got back on sky with only a little time lost.

The basic flow of the interferometric observing is as follows:

1. Observe a flux calibrator: This is a source of known brightness which remains stable with time. If you compare the known brightness of the source with what you measure, you can determine how bright the science target is.
2. Observe a phase calibrator: Because we are observing radio waves, you can measure the amplitude and the phase of the wave. Measuring the phase is crucial for interferometry (more on that another time). But the atmosphere has an effect on the phase and can can change it. So, by measuring an object with stable (0) phase (a point source), you can correct for changes in the atmosphere which would corrupt your data.
3. Take science data: Finally, after calibrations (note that you can add in other calibrations depending on what your science goals are: polarization for example), you can finally point at the source and begin taking data on the galaxy of interest.

Of course, the atmosphere is changing with time. There are clouds going by, wind, thermal effects, etc. These can all change the phase of the incoming radio waves. So periodically you need to stop taking data on your source and re-observe the phase calibrator so you can see how the phase changed. If you have measurements of the phase over the whole time of your observation, you can track the effect the atmosphere would have on the measured phases of the interesting galaxy. The whole time you’re observing you are moving between the galaxy of interest and a phase calibrator. How often you need to check the phases depends on what wavelength you are observing and what science you want to do.

I am in the middle of the observing run now, and the computer controlling the telescope is alternating looking at the target galaxy and observing the phase calibrator. I am sitting comfortably in the control room, monitoring the progress.

Yesterday, before observing I took a minute to walk to one of the nearby dishes. Seeing a 45m diameter wire mesh dish is pretty impressive. There was a bit of a breeze as well, and you can hear it blowing across the mesh. There is apparently wildlife around, including snakes, scorpions, and even the occasional leopard! I’ve yet to run across any though. The facilities here are quite nice as well.

This is the first of two sessions on the telescope. I have my final one this coming Friday to look at another galaxy. I’ll spend the intervening time analyzing the data taken tonight.

More pictures from the GMRT are online here: NCRA, GMRT, and Travel on flickr

Related posts:

1. More 1.4 GHz Observing
2. Observing at the GMRT (Part II)
3. Testing an Interaction Scenario

Yesterday was a long day. I ended up only getting about an hour or two of sleep, being too stressed about missing my train to actually rest. I finally got out of bed around 0530, showered, and finished putting everything in my bag. I was out of the hotel by 0615, walking to Victoria Terminus to catch my 0645 train.

My worry about finding the right train turned out to be for naught, as a large board showed the departures and the tracks were easy to find. I ended up walking most of the length of the train to get to my car. I had arrived about 20 minutes early an the car was mostly empty. I put my (far too heavy) bad on the rack above my seat and settled in for the trip.

The windows were tinted copper to keep the car cool (it was an air conditioned car), and there was an electrical outlet for almost every row of seats! I was surprised to see that. The windows were nice from an energy efficiency standpoint, but made taking pictures difficult due to the color change and the dimming.

The train ride was interesting, with lots of varied terrain. We of course started in Mumbai, which showed a unique combination of nice buildings & skyscrapers, intermixed with slums. Our first stop on the line was further North in Mumbai, and the influx of passengers here practically filled the car.

There were often people walking along the tracks, particularly near the slums. As we turned towards the East, the terrain became more agricultural. There were lots of rice paddys along the way, with small villages or even single houses nearby. A few house-sized stacks of bricks were passed as well. Presumably these were in the process of drying (although I’m not sure how that happens in the Monsoon season, so perhaps they are stacked for another reason).

The nicest scenery of the trip was when we climbed over a mountain pass. We went through many tunnels in the mountain on the way though. Between the tunnels there were often gorgeous waterfalls and cascades falling through rocky ravines in lush green hillsides.

I enjoyed the train ride. It is a nice way to see the countryside while still making decent time. You can see an interesting snapshot of lives along the way too. I saw a man tending cows, another who looked like he was thrashing wheat. But you only see that two second view of that person’s life.

After a little over three hours, the train reached the town of Pune. It is a decently large town (1 million people). The whole train exited at this point and the platform was crowded with people. I worked my way out of the station with the crowd. Almost immediately I was approached by a rickshaw driver trying to give me a ride. However, transportation had already been arranged by the National Centre for Radio Astrophysics (NCRA), so I declined.

I found the driver and he took me through town to the NCRA. I arrived around 1030, but it felt like late afternoon as I’d been up for so long. I checked in and got my room. Then met with a student here to prepare for my observations. I am looking forward to getting to the telescope and doing some observing!

The rest of the pictures from the train ride are available here: Mumbai – Pune Train on flickr

Related posts:

1. Mumbai: Day 1
2. Traffic in Pune
3. Mumbai: Day 2 – Elephanta Island & Caves

It’s early in the morning and again I can’t sleep. I had a much better day today, both in terms of success adventuring and being social. However, the social event, coupled with a taxi driver who couldn’t find my hotel and then tried to rip me off, made for a late evening. I finally finished packing around 0130! Not much time for sleep before my 0645 train.

It was raining again in the morning so I lounged around a bit in the room. Around 10am the rain died down and I ventured outside. Again my goal was Elephanta Island.

Shortly after leaving the hotel, the clouds almost broke and it was very bright. Almost enough to make me wish I had brought my sunglasses! I arrived at the Gateway of India to find a much more active scene than the previous day. Many people milling about in the (almost) sunshine. I fended off many people attempting to sell me guided tours, but was caught off guard by a man purporting to be some sort of mystic or holy man. He gave me a flower, some candy, tied a string around my wrist and rubbed something on my forehead, all the while telling me I would be a lucky man. Then naturally, he asked for money.

When I decided I had taken enough pictures of Gateway in the sunshine, I purchased a ticket for a boat to Elephanta Island to see Elephanta Caves. Rs 130 to get on the boat and another 10 to sit on the uncovered top level. It seemed like a good idea until the downpour started again. Oh well, a little water never hurt anyone.

Fortunately it eased off as we got into the 1 hour trip to the island. The boat trip out was great fun. We started off passing by the Naval Base, where stern looking guards watched the bay from short towers along the shoreline. Further north we could see a fortified bunker and several Indian Navy ships in the background, including an aircraft carrier.

Continuing out we saw around 20 of what appeared to be salvage or repair ships, with low hulls rounded at one end and a huge winch at the other. Closer to the island we saw several oil ships docked at transfer stations for the refinery. There was an oil spill in this area recently and signs of it were visible on the walk up to the caves at Elephanta island.

After about an hour on the boat we docked at the island and disembarked. Anyone who looked remotely non-local was quickly swarmed by people eager to sell us umbrellas or their services as a guide.

After paying a Rs 5 tax to walk around the island, I began climbing the steps towards the caves (120 according to the first person who tried to sell his services as a guide). The whole way was lined with vendors selling their wares. I stopped and purchased a few gifts and a set of coasters for myself. I tried haggling, with some success. I need to hone that skill.

I finally arrived at the top of the steps where a small guard shack marked the entrance to the UNSECO world heritage site. Rs 250 for foreigners and I was in. There are five caves, each excavated to different degrees. The first is the most impressive, with a large cavern carved into the rock and many images of Hindu gods carved into the walls. Certainly a marvel of human achievement, given they were carved over 1500 years ago.

I got numerous pictures of the various caves and the statues and rooms in them. It was interesting to see that as you moved up the hill, the offers for guides became less and less expensive. Inside the site, the guards were offering tours for Rs 50 (despite the signs outside indicating the government provides free guides). I spent around two hours at the caves walking around and taking pictures (and waiting out the occasional storm).

I walked back down the purported 120 steps (I neglected to count them myself) and stopped at a small restaurant for some egg curry before boarding the boat back to Mumbai. Much of the ride back was spent chatting with a Brit who was spending 3 months traveling through the whole of India. He was about a month in and had just arrived in Mumbai.

After returning, I met up with a friend of a friend for dinner and a beer. It was great to get out and be social after spending a few days doing things alone. He is also a former RIT student, so we reminisced about that and Rochester, NY.

To get me back to my hotel, we flagged down a taxi and I hopped in. I should have known the fact that he didn’t honk like every other driver in the city didn’t bode well…

He got lost and took me to several hotels, none of which were mine. Finally, we got to somewhere I recognized and I pointed the way to my hotel. Then, to my surprise he demanded payment of Rs 1000 for the trip! It was Rs 300 to go the opposite way. Eventually we settled at RS 600. He was trying to charge me for all the back and forth driving he did. Ah, the adventures of traveling!

The rest of the pictures from are online here: Elephanta Island on flickr

Related posts:

1. Mumbai: Day 1
2. Train from Mumbai to Pune

02:30 19 August 2010

Yesterday was a bit of an adventure, partly due to the monsoon rains and partly due to my lack of a backup plan. My original intention was to go to Gateway of India and catch a boat to Elephanta Island. I expected this to consume most of my day.

I left the hotel around 0900, planning to walk to the Gateway, about 1 mile down the road. Most of the walk is along high walls of various Indian Government facilities: the mint, the Mahadaresh Police Force, and the Naval Yards. The system of walls is punctuated with frequent entryways for those certified. Each guarded by several men with assault rifles.

After about half an hour of walking in the rain I arrived at the nearly deserted Gateway of India. There were a few people milling around in the large square but for the most part it was empty. From here I was going to take a boat from here to Elephanta Island to see the caves. Due to the heavy rains the boats were not operating at the time, leaving me without a plan.

So, I spent much of the day wandering around town. After taking a few more pictures at the Gateway, I briefly walked around the Taj hotel before moving on to Chhatrapati Shivaji Maharaj Vastu Sangrahalaya (formerly Prince of Wales museum). I arrived about 30 minutes before opening time, so I pressed onward.

Next I came to a slightly barricaded area with a large police presence, including a van of “commandos” carrying M-16s. This area turned out to be the Mumbai financial district. A large bull statue, reminiscent of Wall St in New York City, decorated the plaza in front of the stock market.

The streets had been fairly quiet until now, but just before 1000 people began flooding the streets, all walking towards the district. Rush hour! Throngs of people crossing the streets when traffic stopped, followed by car horns, aimed at the pedestrian stragglers when the light turned green. I stood and watched several cycles of the light, slightly overwhelmed at the scale of things and the downpour I had just walked through.

After watching the “commuters”, I walked back towards the museum which was open now. But, despite the rain, I didn’t feel like spending a lot of my day inside a museum when there was city to see. I walked North again, this time headed for the University of Mumbai. The architecture of the University is very interesting. Unfortunately I was only able to take a few pictures. I was impressed by the well maintained grounds around the building, but also by the small size (occupied less than a city block).

After a loop around the University and past the Oval Maiden (large open park), I continued South, intending to return to the Taj hotel and see if the boats to Elephanta Island were running again. However, I ended up slightly West of where I expected and spent a long time walking through Colaba, eventually finding myself at a sign proclaiming I was entering a “Secure Defense Area”, where I opted to turn around and retrace my steps.

This walk through Colaba was interesting. It was my first exposure to the slums Mumbai is known for. They made a seamless transition between “normal” business establishments and back. Some of the slums even appeared to have satellite dishes mounted to exterior walls. The area I saw was small and bordered the ocean. Just past the slums was a large collection of boats, mostly under large tarps. Continuing on through Colaba, I passed many tailor shops. Although I didn’t stop, it appeared they were very inexpensive.. Rs 40 for a dress shirt! (About $1).

I also saw several cows tied up in various places as I walked around. Interesting to see the contrast between the 2nd most populated city on earth and cows in the heart of it.

As I began to retrace my steps to return to a familiar area, my feet began to hurt. Three hours of walking with wet socks and shoes was starting to take their toll. I decided to cut my adventuring short and return to the hotel to dry off and form a plan for the afternoon.

I had taken my jacket off because the rain had (mostly) stopped. As I turned to head back it began to mist, then drizzle, then rain. The gradual increase in intensity of the storm meant I was soaking wet by the time I returned to the hotel a half hour later. Just like the proverbial frog in a pan of slowly heated water. My soggy return elicited amused smiles from the hotel staff.

The morning’s adventures had me quite overwhelmed. My plans hadn’t worked out and I was soaking wet. It would be a lie to say I wasn’t tempted to hide out in my room for the rest of the day. But, since I only have two days here I decided I had to at least do something.

After a quick rest and change of clothes I decided a safe thing to do was to go shopping. I needed a power adapter for my laptop and also wanted to pick up some gifts for people while I was here. I figured shopping would be a relaxing an manageable activity for the overwhelmed soul.

By the time I returned it was nearly 1600. Again, removing wet layers (I really need to buy an umbrella, not taking rain pants was a mistake), I settled in to relax for a little while. I logged onto the internet and chatted briefly with some folks while I plotted for dinner. The idea of eating at the restaurant felt safe, but I was determined to not succumb to that. I had heard of “bombay duck” (a fried fish) and was interested in trying it, so I found a seafood restaurant near the hotel. Just before 1800 I put on my (mostly) dry clothes and forged on into the rain. The restaurant (Bhatra Excellensea) was a bit tricky to find, but I was eventually successful.

I ordered the Bombay Duck and some garlic naan to go with my beer. After snacking on some bread and peanuts, my food arrived. Four pieces of battered and fried fish with a slightly spicy curry. Mmmm, my mouth is watering again just thinking about it. I must say, it was very good. I am tempted to get it again, but I must be adventurous!

After the meal I returned to the hotel, feeling very tired. I went to be just before 2100. I slept very soundly for a while, waking up around 0200. Only one night, so I should not expect to be over the jet-lag. But now (0340) I am going to try and get some more sleep, hopefully making it close to a full night’s worth. I don’t yet have plans for tomorrow, but I may return to the Gateway to see if the boats to Elephanta are operating. Then I might poke my head into the museum or explore other areas of the city. High tea at the Taj sounds interesting too.

More pictures are available here: Mumbai on flickr

Related posts:

1. Mumbai: Day 2 – Elephanta Island & Caves
2. Train from Mumbai to Pune
3. Groningen

I had an excellent experience with the class. Preparing 2 hours of lectures every day is more than a full-time job, never mind the homeworks, exams, and grading. It was very challenging deciding what to talk about and then implementing that in a lecture. But it was also a lot of fun.

I am transitioning adventures at the moment though, and am returning to full time research. This first step actually involves leaving! I am doing some last preparation for an observing run at the Giant Metrewave Radio Telescope in India. It should be a very exciting trip! I will post pictures through the trip (depending on how often I have internet access).

Related posts:

1. And I thought taking a class was a lot of work…
2. PhD Qualifying Exams Done
3. Dual Purpose Evening

Related posts:

1. Rain, Hail, and Trail

Related posts:

1. Sunset on the Heath
2. Sunset on Lake Reynovia
3. Birds at sunset near Khed