the final minute of liftoff. >> america will continue the dream. >> on wednesday, nasa will launch two u.s. astronauts into space for the first time since the retirement of the space shuttle program in 2011. the azure not will join the current team of two russians and one american on board the international space station. our look at the history of space exploration continues. coming up, the story of teacher and astronaut christa mcauliffe and the ill-fated space shuttle challenger mission. following that, nasa mathematician katherine johnson and her impact on key nasa missions including moon landings. first, a visit to the place responsible for the first ever precise measurement of the distance from the moon to the earth. opened in 1884, the lick observatory in san jose has over 150,000 photographs of the moon. >> james lick was a wealthy

businessman in the san francisco bay area back in the 1800's. his fortune was over $3 million back in the 1860's. and he wanted to be remembered. and george davidson, the president of the california academy of sciences and george madera, an astronomer, who showed him what saturn looked like through a small telescope, were some of the factors that convinced him that a scientific monument that would make great discoveries was the right way to go. so he decided he wanted the greatest telescope superior to any in existence constructed as his memorial and gave about $700,000 of his fortune to form the lick observatory and this telescope is his monument. the construction of this observatory took quite a long time and actually started in the 1870's. mount hamilton was an unoccupied mountain. there was no road to the top.

so they convinced santa clara county to build a first-class road to the top of mount hamilton and that started in 1876. by 1888, the road construction was done and they could finally actually start building this building. and then, by 1886, they finally knew how big the telescope would be. the lenses were done being made and ground to their final figure so they could start constructing this dome. and this dome is large diameter. i do not know exactly how large it is, approximately 100 feet in diameter and it houses a 60-foot long telescope. you'll notice that the telescope is high up so you can't reach the eyepiece easily, but they worked around this problem because the floor i'm standing on was a huge elevator and this floor would go up to the telescope so the astronomer could ride the floor up to whatever place the telescope was and easily look through the eye piece or take the photographic plate data they were taking back in the late 1800's, early

900's. astronomy in the late 1800s and early 1900s, when the observatory was constructed, was going through a heyday of discovery. this telescope, when constructed, was the largest of its kind in the world in 1888. and with it, they were able to make some great early discoveries just in the first few years of this observatory. just first night of science -- just the first night of science observations with this telescope in january of 1888, james keeler, a young astronomer here, looked at saturn and actually discovered a new gas in the rings of saturn now called the antedivision. a couple of years later, emerson barnard used the telescope to discover the fifth moon of jupiter. when he looked through the telescope and discovered the fifth moon, that was a huge discovery.

people didn't know there were more moons around jupiter and it was, in fact, the last moon discovered in our solar system using visual techniques, just looking with a human eyeball through a telescope. all subsequent moons in the solar system since discovered have been discovered hotographically. this is the lick observatory plate vault or photographic plate archive. lick observatory was very influential in the early days of astronomical photography, and we have on the order of 150,000 photographic plates covering over 100 years of astronomical research. today, we do not use photographic plates. we use digital cameras instead. this observatory was a key organization in moving to using digital cameras for astronomical research instead of the old photographic plates. so i'm going to pull a few of the photographic plates so you can see what they look like. lick observatory was prominent

in moon observation so we have any, many plates of the moon from the late 1800's and early 1900's. and this is a plate from 908. and this is a negative image so you can see the moon looks dark and the sky looks white. when it is printed out, it would look like a white moon with the dark background. and these moon plates taken at lick observatory are some of the finest images of the moon in existence. fortunately for that time period

and are routinely used in textbooks today when you're learning about the moon. lick observatory was not only doing research on the moon back in the late 1800's and early 1900s, but we had a key part to play in the apollo 11 mission. buzz aldrin and neil armstrong, put on the moon, on their first trip, what's called the lunar retroreflector. these prisms that if light came in, the light would be sent back along the same path. we, here at lick observatory, used our largest telescope, the shane 120-inch diameter telescope, to shoot a laser at that moon to hit that retrorefractor and send that laser light back to us, which we detected with the same telescope and that yielded the most accurate measurement to the distance of the moon ever done to that point. james lick unfortunately did not get to see his monument finished. he died in 1876 and was originally buried in san

francisco at the masonic cemetery, but his final wish was to be buried at his monument so james lick was disinterred from san francisco in 1887 and einterred at the base of the telescope, so his tomb is at the base of the telescope and the telescope itself is his tombstone. >> with nasa's scheduled wednesday launch of two u.s. astronauts into space for the first time since 2011, we are looking back at the history of space exploration. >> firing chain is armed. >> on-screen is the atlantis, the last of 135 launches of the shuttle program that span from 1981 until 2011. next, the story of christa mcauliffe, one of the crewmember's on board of the ill-fated space shuttle challenger.