ISS ground track plotter

iss_tle.R

library(tidyverse)
library(asteRisk)
library(ggmap)
library(lubridate)

getLatestSpaceData()

iss_tle <- read_file(
    "https://celestrak.com/NORAD/elements/gp.php?CATNR=25544&FORMAT=tle"
) %>%
strsplit(., " *\r\n") %>%
flatten_chr() %>%
parseTLElines()

params <- iss_tle %>% {
    list(
        n0 = `$`(., meanMotion) * ((2 * pi) / (1440)),
        e0 = `$`(., eccentricity),
        i0 = `$`(., inclination) * pi / 180,
        M0 = `$`(., meanAnomaly) * pi / 180,
        omega0 = `$`(., perigeeArgument) * pi / 180,
        OMEGA0 = `$`(., ascension) * pi / 180,
        Bstar = `$`(., Bstar),
        initialDateTime = `$`(., dateTime)
    )
}

progress <- now(tzone = "UTC") %>% {
    t <- as.numeric(. - as.POSIXct(iss_tle$dateTime, tz = "UTC")) * 60
    tibble(
        time = c(seq(-50, 50, by = 1) + t, t),
        val = map(time, ~rlang::inject(sgdp4(!!!params, targetTime = .)))
    )
} %>%
unnest_wider(val)

geodetic <- progress %>%
mutate(
    time = as.POSIXct(iss_tle$dateTime, tz = "UTC") + time * 60,
    p = map(position, ~ .x * 1000),
    a = map2(p, as.character(time), TEMEtoLATLON),
    a = map(a, setNames, c("latitude", "longitude", "altitude")),
    .keep = "none"
) %>%
unnest_wider(a)

ggmap(get_map(c(left = -180, right = 180, bottom = -80, top = 80))) +
geom_point(
    data = geodetic %>% slice(1: n() - 1),
    aes(x = longitude, y = latitude, color = time),
    size = 0.3,
    alpha = 0.8
) +
theme(legend.position = "bottom", legend.key.width = unit(5, "line")) +
geom_point(
    data = geodetic %>% slice(n()),
    aes(x = longitude, y = latitude),
    color = "red",
    shape = 3,
    size = 4
)

geodetic %>% slice(n())