how can I fill the missing values of my data, filling in the days (they are for minutes) and add "nan" to the missing data

Question

thanks in advance, this is the code that i have right now: I have four columns of data, in one it is shown, the TIMESTAMP, the following GLOBALHORZ_avg, DNI_avg and DIFFHORZ_avg, each line should be separated by only one minute, the in the TIMESTAMP column, where I have missing values, I would like it to add the missing TIMESTAMP label (because sometimes the radiation sensor fails and stops taking data) and where data is missing, put NAN, so that I can make matrices with the exact amount of data.

import numpy as np                     #paquete funciones matemáticas
import datetime as dt                  #Formato 
from numpy import nan

#cambiar el nombre de la columna de los data 1
df = pd.read_csv('Dir_Glob_Dif_29dic2020_17mar2022.csv')
df = df.rename(columns=({'Fecha':'TIMESTAMP'}))
df = df.rename(columns=({'RDirecta':'GLOBHORZ_Avg'}))
df = df.rename(columns=({'RGlobal':'DNI_Avg'}))
df = df.rename(columns=({'RDifusa':'DIFFHORZ_Avg'}))

# reading two csv files
dat_crud_2 =df
dat_crud_1 = pd.read_csv('datos_crudos_b_TH_GHI_DNI_DHI.csv')

#para unir los archivos
frames = [dat_crud_1,dat_crud_2]
result = pd.concat(frames)```