Anniversary of the end of Sputnik 1

Happy 2023 to everyone. I notice that I did not blog once in December. I am not planning to stop, but my pace has certainly languished. I will probably not return to the biweekly pace I tended to keep for much of the last couple of years. No resolutions here, but we will see what the New Year brings.

I was looking for a historical event to post on the right sidebar, and it turns out today is the 65th anniversary of the death of Sputnik 1, first satellite into space, launched as intended during the International Geophysical Year. In a previous post I noted the anniversary of Sputnik 1's launch on Oct 4, 1957, three months into the IGY. Another post filled in additional technical details of the mission. Three months later, on Jan. 4, 1958, after 1,440 orbits each lasting 90 minutes, the satellite burned up as it re-entered the Earth's atmosphere.

Here is a cute video on how satellites stay in orbit, and why their orbits eventually decay.

By the way, the European Space agency defines low Earth orbit (LEO), where atmospheric drag degrades satellite orbits, as an elevation of less than 1,000 km above the Earth's surface. Sputnik 1's orbital elevation ranged from 215 km at perigee to 939 km at apogee, so it qualified as being in LEO.

Forbes.com actually posted an article in 2018, This Is Why Sputnik Crashed Back To Earth After Only 3 Months, by Ethan Siegel. It states that even though Sputnik's orbit was above the so-called Kármán line, hence in outer space, "Such disaster [of a satellite's demise] is inevitable due to satellite drag, which is a way to quantify how much speed a satellite loses over time due to the atmospheric particles it runs into at high relative speeds. Any satellite in low-Earth orbit will have a lifespan ranging from a few months up to a few decades, but no longer than that."

I came across an interesting web site, the Index of Objects Launched into Outer Space (including Earth satellites) from the United Nations Office for Outer Space Affairs. I could not seem to sort the table, but using the filter by launch year, I was able to obtain and graph (I love making graphs!) the number of launches by year, starting with the first two Sputnik launches in 1958 (see graph below). There are currently 10,100 still in orbit, and 4,176 objects not in orbit. After averaging 131 launches/year from 1965-2015, the number of launches has started going up exponentially, due to the Starlink program of SpaceX, which plans to deploy nearly 12,000 microsatellites to provide Internet access coverage to 45 countries and global mobile phone service. 

Objects launched into space by year (my graph, data from United Nations)

My editor pointed out that one of her favorite podcasts, Planet Money, had  a series, Planet Money Goes To Space, about the relative ease of getting a satellite into space these days.

We've come a long way since that 3-month lifetime of Sputnik 1!