Aupasana (Samskrit : औपासनः) is one of the important Smarta Yajnas performed daily by grihasthas who have been initiated during marriage. Aupasana, which must be performed every day, is commenced in the Grhyagni (Aupasanagni) and it must be preserved throughout one's life. The seven pakayajnas, rites including upanayana and shraaddha, must be conducted in the aupasana fire.
All rites in which the aupasana fire is used and pertain to an individual and his family are "Grhyakarmas". They are related exclusively to the family and are not very elaborate. Even so they are conducive to the good of the world outside also. Grhyasutras deal with such rites. They belong to the Smritis and so are called "Smarta-karmas". The seven Pakayajnas also belong to this category.
The list of seven Pakayajnas according to Apastamba Grhyasutras as elucidated in the commentary of Haradatta, include
तत्र च सप्त पाकयज्ञसंस्थाः - औपासनहोमो, वैश्वदेवं, पार्वण, मष्टका, मासिश्राद्धं, सर्पबलिं, रीशानबलिरिति ।
Other versions of Grhyasutras are present. For example: according to Baudhayana Grhya sutras, the Pakayajnas are
औपासनः ॥ Aupasana
Aupasana can be considered as a enhancement of samidadhanam which is performed by brahmacharis once initiated by Upanayana ceremony.
According to Vachaspatyam Aupasana is given as
उपास्यते प्रतिदिनमित्युपासनो गृह्योऽग्निस्तत्र भवः अण् । गृह्याग्नौ कर्त्तव्ये सायंप्रातर्होमादौ कर्म्मणि । गृह्याग्निश्च विवाहाग्निः ।
That Agni which is worshipped at home everyday, Grhyagni in which the morning and evening homa kriyas are to be performed. Grhyagni is Vivahagni.
Initiation into Aupasana
During vivaha samskara one is initiated to enter the grhasta ashram by setting up the आवसथ्याग्निः ॥ Avasatyaagni to the north of the vedi. (Paaraskara Grhya Sutra Adhyaya 1 Kandika 2 Mantra 1)
आवसथ्याधानं दारकाले १ दायाद्यकाल एकेषाम् २ ॥ āvasathyādhānaṁ dārakālē 1 dāyādyakāla ēkēṣām 2 (Para.Grhy.Sutra. 1.2.1)
Meaning : The setting up of Aavasatya agni is (performed) at the time of wedding. At the time of inheritance according to some.
The son lights his aupasana fire during his marriage from his father's aupasana fire. The son's aupasana fire, like his father's must be maintained throughout his life. Thus, without any break, the sacred fire is kept burning in the family generation after generation.
Normally this fire is located in the north of the hall which accommodates the other Agnikundas . Yajnakunda for this Agni may be circular or square
Rites to be performed in Aupasanagni
- Masika Sraadham
- Parvana Sraadham
Rites to be performed in Loukika Agni
During marriage he receives additional instructions to perform nityakarma. A few features include
- Starting from marriage, a grihasta (along with his wife) offers aahutis twice daily at twilight time (dawn and dusk) in the Aupasanagni, this is also called as Aupasana.
- All the daily ahutis and cooking involves the aupasana fire and pertain exclusively to the individual and his family. Thus, "Grhyakarmas" including the seven pakayajnas involve the aupasana agni or Grhyagni or smarthagani. They are related exclusively to the family and are not very elaborate.
- Aupasana is to be performed by the grihasthas of the three varnas. Valmiki Ramayana in Ayodhya kanda mentions that Sri Ramachandra, a kshatriya, enquires Bharata about tending the Agni in the house.
Meaning : "I hope that a brahmin who is versed in the traditions, who is intelligent and just, employed in your sacred fires, always informs you in time, about a sacrificial fire having been or going to be fed with oblations."
कच्चिद् अग्निषु ते युक्तो विधिज्नो मतिमान् ऋजुः | हुतम् च होष्यमाणम् च काले वेदयते सदा || २-१००-१२ (Valm. Rama. 2.100.12)
- Every grihastha has to maintain the agni until he is prevented by old age or illness or death. In case where he cannot perform it on behalf of him his son, brother or son-in-law may perform the ritual. 
- Performance of nitya agnihotra is mandated to the grihasta men of all three varnas. If due to any reason, a grihasta has not conducted agnihotra rituals, he can do so after performing the praayaschitta vidhis as given in the Srauta sastras.
- As a nityakriya agnihotra, Anuditahomi's perform homa before sunrise and some Uditahomi's after sunset.
- Mantras for conducting Agnihotra are covered in Krishna Yajurveda's Taittiriya Samhita in Kanda 1(the 5th Prapathaka contains the mantras for पुनराधेयम् and अग्न्युपस्थानम् )
- Morning aahutis are made to the deities Surya and Prajapati, while the evening aahutis are made to Agni and Prajapati.
- Nitya agnihotra is not to be performed by an uninitiated bachelor or widows.
- Sri Sri Sri Chandrasekharendra Saraswathi Swamiji, (2000) Hindu Dharma (Collection of Swamiji's Speeches between 1907 to 1994)Mumbai : Bharatiya Vidya Bhavan
- Apastamba Grhyasutras with commentary by Haradatta (Anukula Vritti)
- Vachaspatyam (See Aupasana)
- Paraaskara Grhya Sutras
- Kannan, P. R. Balabodha Sangraha - 3 (Topic Efficacies of Agni Upasana) Kanchi Kaamkoti Peetham
- Venkateswara Rao. Potturi (2010) Paaramaathika Padakosam Hyderabad: Msko Books
- Valmiki Ramayana Ayodhya Kanda Sarga 100
- Purkayastha, Dipanjona (2014) Ph. D Thesis from Assam University : A Study of the Asvalayana srauta sutra with reference to the principal sacrifices
- Taittriya Samhita (Kandam 1 Prapathaka 5)