gsat: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/gsat - from package: predict-gsat

You may install the required package with command apt-get install {package}

Error in other languages:
gsat: bevel nie gevind nie
gsat: comandă negăsită
gsat: comando não encontrado
gsat: commande introuvable
gsat: command not found
gsat: käsku ei ole
gsat: không tìm thấy lệnh
gsat: komanda nerasta
gsat: Kommando nicht gefunden.
gsat: kommandot finns inte
gsat: komut yok
gsat: nie znaleziono polecenia
gsat: níor aimsíodh an t-ordú
gsat: no se encontró la orden
gsat: no s'ha trobat l'ordre
gsat: opdracht niet gevonden
gsat: parancs nem található
gsat: perintah tidak ditemukan
gsat: príkaz nenájdený
gsat: příkaz nenalezen
gsat: команда не найдена
gsat: командата не е открита
gsat: 命令找不到
gsat: コマンドが見つかりません