<PAGE>



                                                                   EXHIBIT 3.3.1

                             AUDIT COMMITTEE CHARTER
                            THORNBURG MORTGAGE, INC.
                             Revised April 23, 2002

         The Audit Committee (the "Committee") is appointed by the Thornburg
Mortgage, Inc (the "Company") Board of Directors (the "Board") to assist the
Board in fulfilling its oversight responsibilities. The Audit Committee and the
Board of Directors have the responsibility to select, evaluate and, where
appropriate, replace the external auditors (the "Auditors"), who are responsible
to the Board and the Audit Committee. The Audit Committee, with the assistance
of Management and the Auditors, will review i) the financial reporting process,
ii) the system of internal controls, iii) the audit process, and iv) the
Company's process for monitoring compliance with laws and regulations. In
performing its duties, the Committee will maintain effective working
relationships with the Board of Directors, Management, and the Auditors. To
effectively perform its role, each Committee member will obtain an understanding
of the responsibilities of Committee membership as outlined in this charter as
well as the Company's business, operations, and risks. The Board has adopted and
approved this charter which will govern the activities of the Audit Committee.

         The Audit Committee shall meet the independence and experience
requirements of the New York Stock Exchange ("NYSE") rules on audit committees.
The Audit Committee shall have at least three members, all of whom are directors
and have no business relationship with the Company (or an affiliate) that may
interfere with the exercise of their independent judgment. If any business
relationship does exist, it will be disclosed to the Board and the Board will
determine if that business relationship might interfere with the director's
exercise of independent judgment. In order to serve on the Audit Committee each
member shall be financially literate. At least one member shall have accounting
or related financial expertise. The Board, based upon the recommendation of the
Nominating Committee, shall appoint the members of the Audit Committee.

         The Audit Committee shall have the authority to request any officer or
employee of the Company or the Company's outside counsel or Auditors to attend a
meeting of the Committee or to meet with any members of, or consultants to, the
Committee. Under special circumstances that may arise, the Committee may request
authority from the Board of Directors to retain special legal counsel, auditors
or other consultants to advise the Committee.

         As a matter of Company policy and as part of the Auditor's annual
engagement agreement, the Company's Auditors will review the interim financial
statements prior to filing its Form 10-Q with the Securities and Exchange
Commission (the "SEC"). The Auditors will be instructed to communicate any
significant unresolved matters arising out of such review to the Audit Committee
or its Chairman, prior to the filing of the Form 10-Q. The Audit Committee shall
report any such unresolved matters to the Board.

         The Audit Committee shall meet with the Auditors at least twice
annually as part of the annual audit process, as described below, and shall meet
with the Auditors in person or telephonically prior to each quarterly Board
meeting to review the quarterly financial statements and the Company's
accounting practices. The Audit Committee shall report on such meetings to the
Board at the next following Board meeting, or earlier, if appropriate.

         The Audit Committee shall have the following responsibilities:

     1.  Annually evaluate the performance of the Auditors, review the
         experience and qualifications of the senior members of the Audit team,
         recommend to the Board the appointment of the Auditors and approve the
         fees to be paid to such Auditors.

     2.  Meet with the Auditors prior to the audit of the annual financial
         statements to review the planning, scope and staffing of the audit.

     3.  Meet with the Auditors to review the annual audited financial
         statements and to discuss the results of the audit, including:

         a.   major issues regarding accounting and auditing principles and
              practices,

         b.   judgments about the quality of the Company's accounting principles
              and underlying estimates,

         c.   the adequacy of internal controls that could significantly affect
              the Company's financial statements,

         d.   any other matters required to be discussed by Statement on
              Auditing Standards No. 61, as amended,
              Communications With Audit Committees, relating to the conduct of
              the audit, and



<PAGE>

         e.   obtain from the Auditors assurance that they have complied with
              Section 10A of the Securities Exchange Act of 1934.

     4.  Recommend to the Board the inclusion of the annual audited financial
         statements in the Annual Report on Form 10-K to be filed with the SEC.

     5.  The Auditors are free to contact the Chairman of the Audit Committee at
         any time to discuss any matter that the Auditors feel needs to be
         brought to the attention of the Audit Committee.

     6.  Annually receive reports and/or letters from the Auditors regarding
         their independence as required by Independence Standards Board Standard
         No. 1. Discuss with the Auditors any disclosed relationships or
         services that may affect the Auditors' independence and, if so
         determined by the Audit Committee, recommend that the Board take
         appropriate action to satisfy itself of the independence of the
         Auditors.

     7.  Review the quarterly financial statements with Management at each
         quarterly Board meeting and review major risk exposures and steps
         Management has taken to monitor and control such exposures.

     8.  Prior to the Company's filing with the SEC and after the Auditors
         review, the Company will distribute [to the Board and the Audit
         Committee] the Annual Report on Form 10-K and Quarterly Reports on Form
         10-Q for review by the Board and the Audit Committee.

     9.  Obtain quarterly reports from Management and, when applicable, annual
         confirmation from the Auditors regarding the compliance of the Company
         and its subsidiaries with applicable REIT requirements, SEC
         requirements and its investment policies.

     10. Annually, review and reassess the adequacy of the Audit Committee
         Charter and recommend any proposed changes to the Board for approval.

     11. Require that the Company's legal counsel disclose at each Board meeting
         the existence of any legal matter that might have a significant impact
         on the Company's financial statements, and notify the members of the
         Audit Committee of any significant legal matter that might arise
         between Board meetings.

     12. Require that the Company make disclosures as required by the SEC and
         NYSE in its annual proxy statement regarding the following:

         a.    audit committee independence,

         b.    that the Company has adopted an Audit Committee Charter, with a
               copy attached every three years, and

         c.    the annual Audit Committee report that the Committee has:

               1.   reviewed and discussed the annual financial statements with
                    Management and recommended their inclusion in the Form 10-K,

               2.   met with the Auditors and discussed the matters related to
                    the conduct of the audit as required under SAS 61, as
                    amended, and

               3.   received written disclosures and a letter from the Auditors
                    and confirmed the Auditors independence.

     13. Require Management to provide written confirmation to the NYSE on audit
         committee member qualifications and related board determinations, as
         well as the review and re-evaluation of the Audit Committee Charter.

     14. Approve the engagement of the Auditors for any services other than
         audit and tax matters, and the fee for such services where the amount
         of the fee is expected to be in excess of $50,000.

Safe Harbor Statement

         While the Audit Committee has the responsibilities and powers set forth
in this Charter, it is not the duty of the Audit Committee to plan or conduct
audits or to determine that the Company's financial statements are complete,
accurate and in accordance with generally accepted accounting principles. That
is the responsibility of Management and the Auditors. Nor is it the duty of the
Audit Committee to conduct investigations, to resolve disagreements, if any,
between Management and the Auditors or to assure compliance with applicable laws
and regulations.