A petitioner will have to face panel if he he has to appear as a petitioner. Here I'm giving the meaning of panel and when it is constituted borrowed from free online Dictionary.

A list of jurors to serve in a particular court or for the trial of a designated action. A group of judges of a lesser number than the entire court convened to decide a case, such as when a nine-member appellate court divides into three, three-member groups, and each group hears and decides cases. A plan in reference to prepaid legal services.

The term open-panel legal services refers to a plan in which legal services are paid for in advance, usually by insurance, but in which members can select their own lawyers. Under a closed panel, all legal services are rendered by a group of attorneys previously chosen by the insurer, the union, or another entity.If you  appreciate this answer please give me a like on my profile.

https://bombayhighcourt.nic.in/libweb/rules/BHCASRulesPDF/BHCASRules04-A.pdf

Thanks Sachin

Its written