hp_sky_ng_sim: 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 CentOS possible default full paths are:

/usr/bin/hp_sky_ng_sim - from package: healpix

You may install the required package with command yum install {package}

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