## 1 Introduction

[2] Since the mid 1990s, High Power-Large Aperture (HPLA) radars such as ALTAIR, Arecibo, EISCAT, and Jicamarca have proven to be excellent tools for conducting meteor research. HPLA radars can detect scatter from the plasma spheres which surround ablating meteoroids. This scatter data can be used to infer meteoroid parameters such as mass, speed, and other properties. For example, *Chau and Woodman* [2004] used Jicamarca 50 MHz radar to show that the detected meteors were concentrated around theEarth's Apex, and *Chau and Galindo* [2008] proved that HPLA radars can observe meteor shower populations. More recently, *Mathews et al*. [2010] reported meteor observations collected with the VHF and UHF Arecibo radars that seemed consistent with meteoroid fragmentation, and *Vertatschitsch et al*. [2011] presented results from a numerical electromagnetic model of fragmentation. These recent investigations show considerable progress in meteor physics using HPLA radars; however, very few studies have been conducted to fully characterize current radar systems in order to correctly infer meteor parameters. One example is the work by *Chau et al*. [2009] which characterized the impact of the antenna beam pattern on the received power of meteor head echoes. Their results indicated that at least 15% of the meteors observed with the 450 MHz Poker Flat incoherent scatter radar were detected from the sidelobes of the antenna. Therefore the power of these meteors had to be corrected by about ~20 dB to be considered that these events were coming from the main beam of the antenna. These corrections are needed in order to apply current techniques to extract meteor information from the received power [*Close et al*., 2004; *Janches et al*., 2009].

[3] In this paper we assess the role that the ambiguity function plays on the characterization of SNR from meteor head echoes. This analysis is presented by expressing the radar equation for meteor head echoes in terms of the ambiguity function (AF) [*Woodman*, 1991; *Milla and Kudeki*, 2006] of the transmitted pulse envelope and the filter impulse response of the radar receiver. Our results show that any meteor SNR, i.e., SNR collected from a meteor head echo, exhibit temporal ripples to various degrees. These ripples illustrate the importance of obtaining an accurate model of a radar system in order to correctly estimate meteor SNR and subsequently infer other meteor parameters from the SNR. Our theoretical findings are verified by using experimental data collected with the Jicamarca radar and simulated data obtained by replicating the acquisition system of Jicamarca. Additionally, a statistical study on actual meteor data reveals that at least 14% of the population collected each day at Jicamarca exhibit these ripples. On the remaining 86% of events, the ripples cannot be distinguished due to noise, contamination from other sources of scattering (i.e., nonspecular echoes), and ensemble average applied to the data. Therefore any approach such as inversion techniques to infer unbiased meteor parameters must account for the effect of these temporal ripples.

[4] Our paper is organized as follows: Section 2 describes the radar equation for meteor head echoes and presents the AF for Jicamarca HPLA radar receiver. Section 3 shows two meteor head echoes detected with Jicamarca and describes the features observed in their SNR by using the AF analysis. In addition, we present a statistical study of 3 days of meteor observations conducted at Jicamarca, where we show that at least 14% of actual meteor data exhibit the temporal ripples analyzed in this paper. In section 4, we present a simulator of the Jicamarca radar receiver. In section 5, we discuss the role of radar parameters that affect the shape and amplitude of the ripples. Finally, we provide a summary of this research in section 6.