Contact Mystery Cache

Welcome to Contact - a puzzle inspired by Carl Sagan’s novel “Contact” which was later adapted into a film of the same name. The story is my favourite piece of science fiction and thus, I feel it is deserving of a cache. Published coordinates are bogus, as with most mystery caches. 

“Another night of data collection… I hope the weather stays good”, Ellie thought to herself. When it comes to using the telescope, time is of the essence. Hundreds of research projects bid for telescope time every year, and only a lucky few actually win the lottery, so to speak.

Her partner enters the coordinates for the first of their targets for the night, and they wait for the telescope to adjust itself. The behemoth of a telescope accedes to the command of the astronomers and slowly adjusts the telescope’s line of sight.

As the gears turn, Ellie looks out the window into the night sky. She always felt alone since the passing of her father and her greatest mentor, who had first brought her to the telescope when she was only six. She remembered how impressed she was when she saw the telescope’s dish, built into a deep valley in the mountains. Today, she still counts herself impressed every day she steps into the control room.

“Truly an engineering marvel”, she lamented, “and a pity that no one wants builds more of these beauties”. Funding for the search for extra-terrestrial intelligence is erratic and she has done her level best to convince others that this was a worthwhile endeavour.  

As the signals from the distant star cluster streamed in at last, she recalled the times her father taught her to tune the family radio to listen to white noise, and her amazement when he told her that the signals were from distant galaxies…

Her thoughts were interrupted by set of loud low frequency sounds emitted by their device’s speakers. It seemed as if the machine had come to life and she was listening to its heartbeat.

“Wow, what is that?” Ellie asked her colleague.

“A very strong periodic signal of some sort… though, it’s not as regular as we’d expect from a pulsar.”

“The signals… what frequency are we listening in to right now?”

“In the range of 2380 MHz. There’s another set”, her colleague said while turning a knob, “at a slightly lower frequency.”  

The pulses kept streaming in and the machine announced the arrival of each with a mechanical pulse. They tried to determine the period between each high and low frequency pulses, but there seems to be no way to predict which pulse would arrive next. After two minutes, the pulses stopped as suddenly as they began. The two astronomers looked at the data collected (A = lower frequency pulse and B = higher frequency pulse):

FIRST CONTACT

ABAAABAAAAAAAAAAAAAAAAAABAABAAABAAABAAABA

As they looked for a pattern, the pulses started streaming in again. They counter-checked the incoming pulses with the first set: the first one hundred are precisely the same, and so were the next one hundred, and the next…

“Are you sure we have not pointed our telescope at some TV satellite in orbit?” enquired Ellie

“I’ve checked. There’s nothing between us and the deep dark sky.”

“If we’re pointing the telescope at nothing man-made… how can this be? Unless…”

“No, you’ve got to be kiddi… No, wait a minute, it ca-ca-can’t… I thought that was just a random shot in the dark. Just a test of our capabilites…”

“I remember that day now… I – I - I can’t believe it. A reply? Have we really managed to establish contact?”