# Introduction

Solar System bodies are commonly used as primary flux calibrators in radio astronomy.

Calibration of 30m data relies on good models of the primary calibrators. Main primary calibrators are Uranus and Mars. For heterodyne observations (with EMIR), antenna temperatures (TA* scale) are determined from regular hot/cold/sky calibrations done about every 15min. The scaling to main beam temperatures is done offline using existing tables of main beam and forward efficiencies. The staff is observing primary and secondary calibrators a few times per year. The main beam efficiencies (together with aperture efficiencies, Jy/K factors, HPBWs) are derived from night time observations of primary calibrators. Observers are informed about the current efficiencies via a public wiki page: https://publicwiki.iram.es/Iram30mEfficiencies. Updated numbers are in preparation. The flux stability of primary and secondary calibrators for 1985-2005 is discussed in Kramer, Moreno and Greve (2008, https://arxiv.org/abs/0801.4452). On the other hand, NIKA2 data are calibrated to the mJy/beam scale by regular observations of primary and secondary calibrators every few hours (see https://www.iram.fr/ gildas/dist/piic-dafs.pdf and Perotto et al. 2020). ASTRO has been used for the planetary brightness temperatures and source fluxes.

For NOEMA, antenna efficiencies (Jy/K) during each individual track are determined through observations of secondary calibrators (mostly MWC349 and LKH101). The fluxes of the primary calibrators are measured during dedicated sessions in which they are observed together with planets (Uranus, Neptune, Mars). Also, planetary observations were used to assess the single-dish efficiencies of the NOEMA antennas (mostly Mars).

In the framework of the EHT collaboration, planet observations are also used to define the Jy/K scales of the stations.

The flux of planets is computed by ASTRO when using the PLANET command. The present (a.k.a. Legacy) implementation was implemented more than 30 years ago and never updated since then.

The accuracy of models of the primary calibrators have greatly improved over the past years to about 5% absolute accuracy, rendering it important to update ASTRO.

In the present document we present a new implementation we plan de distribute in 2025 and its impact on the planet fluxes computed by ASTRO. We also compare the proposed ASTRO implementation to what is done in CASA, for ALMA flux calibration.